Use the Dockerfile COPY instead of docker cp (#10943)

## Problem
We use `docker cp` to copy the files required for the extension tests
now.
It causes problems if we run older images with the newer source tree.
## Summary of changes
Copying the files was moved to the compute Dockerfile.

.dockerignore

@@ -14,6 +14,7 @@
 !compute/
 !compute_tools/
 !control_plane/
+!docker-compose/ext-src
 !libs/
 !pageserver/
 !pgxn/

compute/compute-node.Dockerfile

@@ -1818,7 +1818,7 @@ RUN make PG_VERSION="${PG_VERSION:?}" -C compute
 
 FROM pg-build AS extension-tests
 ARG PG_VERSION
-RUN mkdir /ext-src
+COPY docker-compose/ext-src/ /ext-src/
 
 COPY --from=pg-build /postgres /postgres
 #COPY --from=postgis-src /ext-src/ /ext-src/

docker-compose/docker_compose_test.sh

@@ -51,8 +51,6 @@ for pg_version in ${TEST_VERSION_ONLY-14 15 16 17}; do
     done
 
     if [ $pg_version -ge 16 ]; then
-        docker cp ext-src $TEST_CONTAINER_NAME:/
-        docker exec $TEST_CONTAINER_NAME bash -c "apt update && apt install -y libtap-parser-sourcehandler-pgtap-perl"
         # This is required for the pg_hint_plan test, to prevent flaky log message causing the test to fail
         # It cannot be moved to Dockerfile now because the database directory is created after the start of the container
         echo Adding dummy config

docker-compose/test_extensions_upgrade.sh

@@ -57,7 +57,6 @@ new_vers=$(docker compose exec neon-test-extensions psql -Aqt -d contrib_regress
 docker compose --profile test-extensions down
 TAG=${OLDTAG} docker compose --profile test-extensions up --quiet-pull --build -d --force-recreate
 wait_for_ready
-docker compose cp  ext-src neon-test-extensions:/
 docker compose exec neon-test-extensions psql -c "DROP DATABASE IF EXISTS contrib_regression"
 docker compose exec neon-test-extensions psql -c "CREATE DATABASE contrib_regression"
 docker compose exec neon-test-extensions psql -c "CREATE DATABASE pgtap_regression"