Pin actions/checkout Dependency to Specific Commit Hash

It's a bit silly, because if we can't trust GitHub, what are we doing here?
But OSSF complains about it, so let's fix it.

.github/workflows/dev-long-tests.yml

@@ -13,7 +13,7 @@ jobs:
   make-all:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: make all
       run: make all
 
@@ -24,52 +24,52 @@ jobs:
       DEVNULLRIGHTS: 1
       READFROMBLOCKDEVICE: 1
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: make test
       run: make test
 
   # lasts ~26mn
   make-test-osx:
     runs-on: macos-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: OS-X test
       run: make test # make -c lib all doesn't work because of the fact that it's not a tty
 
   no-intrinsics-fuzztest:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: no intrinsics fuzztest
       run: MOREFLAGS="-DZSTD_NO_INTRINSICS" make -C tests fuzztest
 
   tsan-zstreamtest:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: thread sanitizer zstreamtest
       run: CC=clang ZSTREAM_TESTTIME=-T3mn make tsan-test-zstream
 
   ubsan-zstreamtest:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: undefined behavior sanitizer zstreamtest
       run: CC=clang make uasan-test-zstream
 
   # lasts ~15mn
   tsan-fuzztest:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: thread sanitizer fuzztest
       run: CC=clang make tsan-fuzztest
 
   # lasts ~23mn
   gcc-8-asan-ubsan-testzstd:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: gcc-8 + ASan + UBSan + Test Zstd
       # See https://askubuntu.com/a/1428822
       run: |
@@ -81,14 +81,14 @@ jobs:
   clang-asan-ubsan-testzstd:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: clang + ASan + UBSan + Test Zstd
       run: CC=clang make -j uasan-test-zstd </dev/null V=1
 
   gcc-asan-ubsan-testzstd-32bit:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: ASan + UBSan + Test Zstd, 32bit mode
       run: |
         sudo apt-get -qqq update
@@ -102,7 +102,7 @@ jobs:
   gcc-8-asan-ubsan-fuzz:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: gcc-8 + ASan + UBSan + Fuzz Test
       # See https://askubuntu.com/a/1428822
       run: |
@@ -114,14 +114,14 @@ jobs:
   clang-asan-ubsan-fuzz:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: clang + ASan + UBSan + Fuzz Test
       run: CC=clang FUZZER_FLAGS="--long-tests" make clean uasan-fuzztest
 
   gcc-asan-ubsan-fuzz32:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: ASan + UBSan + Fuzz Test 32bit
       run: |
         sudo apt-get -qqq update
@@ -131,7 +131,7 @@ jobs:
   clang-asan-ubsan-fuzz32:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: clang + ASan + UBSan + Fuzz Test 32bit
       run: |
         sudo apt-get -qqq update
@@ -141,28 +141,28 @@ jobs:
   asan-ubsan-regression:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: ASan + UBSan + Regression Test
       run: make -j uasanregressiontest
 
   clang-ubsan-regression:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: clang + ASan + UBSan + Regression Test
       run: CC=clang make -j uasanregressiontest
 
   msan-regression:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: MSan + Regression Test
       run: make -j msanregressiontest
 
   clang-msan-fuzz:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: clang + MSan + Fuzz Test
       run: |
         sudo apt-get -qqq update
@@ -173,7 +173,7 @@ jobs:
   clang-msan-testzstd:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: clang + MSan + Test Zstd
       run: |
         sudo apt-get update
@@ -183,7 +183,7 @@ jobs:
   armfuzz:
       runs-on: ubuntu-latest
       steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
       - name: Qemu ARM emulation + Fuzz Test
         run: |
           sudo apt-get -qqq update
@@ -193,7 +193,7 @@ jobs:
   valgrind-fuzz-test:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: valgrind + fuzz test stack mode    # ~ 7mn
       shell: 'script -q -e -c "bash {0}"'
       run: |
@@ -213,7 +213,7 @@ jobs:
           { compiler: gcc, platform: x64, action: test, script: ""},
         ]
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b # tag=v3
     - name: Mingw long test
       run: |
         $env:PATH_ORIGINAL = $env:PATH