deps: delete deps/v8/third_party/zlib

We currently have two copies of Chromium's zlib: one in deps/zlib and
another in deps/v8/third_party/zlib. This has a couple of disadvantages:

1. There is an additional cost to keeping both dependencies up-to-date,
   and in fact they were already out-of-sync (see the refs).

2. People who compile with --shared-zlib (i.e. distro maintainers) will
   probably not be thrilled to learn that there is still a copy of zlib
   inside.

3. It's aesthetically unpleasing.

This diff (per discussion in the refs) centralizes on deps/zlib and
deletes deps/v8/third_party/zlib. That requires changing the include
headers in two files in deps/v8/src, which was pretty straightforward.

When the user requests compiling with a shared zlib build, we still need
to compile the contents of deps/zlib/google. This is not ideal but it's
also not a change in behavior: prior to this diff those files were
being compiled in the deps/v8/third_party/zlib version.

I tested this on Linux with the default build and a --shared-zlib build.
I checked that the shared-zlib build dynamically linked zlib according
to ldd, and that the regular build did not. I would appreciate if the
reviewers could suggest some other build configurations to try.

Refs: nodejs#47145
Refs: nodejs#47157

common.gypi

@@ -36,7 +36,7 @@
 
     # Reset this number to 0 on major V8 upgrades.
     # Increment by one for each non-official patch applied to deps/v8.
-    'v8_embedder_string': '-node.3',
+    'v8_embedder_string': '-node.4',
 
     ##### V8 defaults for Node.js #####
 

deps/v8/src/deoptimizer/translation-array.cc

@@ -9,7 +9,7 @@
 #include "src/objects/fixed-array-inl.h"
 
 #ifdef V8_USE_ZLIB
-#include "third_party/zlib/google/compression_utils_portable.h"
+#include "compression_utils_portable.h"
 #endif  // V8_USE_ZLIB
 
 namespace v8 {

deps/v8/src/snapshot/snapshot-utils.cc

@@ -7,7 +7,7 @@
 #include "src/base/sanitizer/msan.h"
 
 #ifdef V8_USE_ZLIB
-#include "third_party/zlib/zlib.h"
+#include "zlib.h"
 #endif
 
 namespace v8 {