Extract neon and neon_test_utils from postgres repo (#2325)

* Extract neon and neon_test_utils from postgres repo
* Remove neon from vendored postgres repo, and fix build_and_test.yml
* Move EmitWarningsOnPlaceholders to end of _PG_init in neon.c (from libpagestore.c)
* Fix Makefile location comments
* remove Makefile EXTRA_INSTALL flag
* Update Dockerfile.compute-node to build and include the neon extension

.github/workflows/build_and_test.yml

@@ -136,6 +136,10 @@ jobs:
         run: mold -run make postgres -j$(nproc)
         shell: bash -euxo pipefail {0}
 
+      - name: Build neon extensions
+        run: mold -run make neon-pg-ext -j$(nproc)
+        shell: bash -euxo pipefail {0}
+
       - name: Run cargo build
         run: |
           ${cov_prefix} mold -run cargo build $CARGO_FLAGS --features failpoints --bins --tests

.github/workflows/codestyle.yml

@@ -81,6 +81,9 @@ jobs:
         if: steps.cache_pg.outputs.cache-hit != 'true'
         run: make postgres
 
+      - name: Build neon extensions
+        run: make neon-pg-ext
+
       # Plain configure output can contain weird errors like 'error: C compiler cannot create executables'
       # and the real cause will be inside config.log
       - name: Print configure logs in case of failure