bootstrap a plrust-tests create

The new `plrust-tests` create is a standalone pgrx crate that only
contains the unit tests from `plrust`.  These were copied over verbatim.

To run the tests:

```shell
$ cd plrust-tests
$ ./run-tests.sh pgXX [test_name]
```

Author: eeeebbbbrrrr

Cargo.lock

@@ -3,6 +3,7 @@ resolver = "2"
 members = [
     "plrust",
     "plrust-trusted-pgrx",
+    "plrust-tests",    
 ]
 exclude = ["plrustc"]#, "builder"]
 

Cargo.toml

@@ -0,0 +1,24 @@
+[package]
+name = "plrust-tests"
+version = "0.0.0"
+edition = "2021"
+
+[lib]
+crate-type = ["cdylib"]
+
+[features]
+default = ["pg13"]
+pg13 = ["pgrx/pg13", "pgrx-tests/pg13" ]
+pg14 = ["pgrx/pg14", "pgrx-tests/pg14" ]
+pg15 = ["pgrx/pg15", "pgrx-tests/pg15" ]
+pg_test = []
+
+[dependencies]
+pgrx = "=0.9.5"
+tempdir = "0.3.7"
+once_cell = "1.18.0"
+
+[dev-dependencies]
+pgrx-tests = "=0.9.5"
+tempdir = "0.3.7"
+once_cell = "1.18.0"

plrust-tests/Cargo.toml

@@ -0,0 +1,6 @@
+comment = 'plrust_tests:  Created by pgrx'
+default_version = '@CARGO_VERSION@'
+module_pathname = '$libdir/plrust_tests'
+relocatable = false
+superuser = true
+requires = 'plrust'

plrust-tests/plrust_tests.control

@@ -0,0 +1,28 @@
+#! /bin/bash
+
+VERSION=$1
+
+if [ -z ${VERSION} ]; then
+	echo "usage:  ./run-tests.sh pgXX [test-name]"
+	exit 1
+fi
+
+TEST_DIR=`pwd`
+
+# install the plrust extension into the pgrx-managed postgres
+echo "============================"
+echo " installing plrust"
+echo
+cd ../plrust
+echo "\q" | cargo pgrx run ${VERSION}
+
+# run the test suite from this crate
+cd ${TEST_DIR}
+
+echo
+echo "============================"
+echo " running plrust-tests suite"
+echo
+
+cargo pgrx test ${VERSION} $2
+