[SYCL] Add ABI symbols tests against release branch (#19860)

Before this PR our approach was to have
`sycl_symbols_[linux|windows]-sycl.dump` files in trunk that always
capture the current state of symbols exported from
`libsycl.so`/`sycl.dll` We highlighted added/removed symbols separately
and considered "added" symbols as being OK while "removed" meant an ABI
break. That works fine by is a bit too verbose. Also, not all "removed"
are bad. If we've just added a symbol in a previous commit and are
reverting it now, the backward ABI compatibility against the last
release isn't being broken.

I don't think we promise any backward compatibility between arbitrary
builds in the trunk (`origin/sycl`), only the compatibility against
previous official minor releases with the same major version.

This PR adds two more tests that track what we promise better. I've
modified our `sycl/tools/abi_check.py` to allow ignoring "added" symbols
and only check against symbols that are being removed. I've also copied
`sycl_symbols*.dump` from the `sycl-rel-6_3` branch into the trunk under
`sycl_symbols*-sycl-rel-6_3.dump` names and started running the testing
for them in that new mode. Those **must** never fail, unless we're
incrementing the major version or the break is intentional and approved
(hence dedicated `CODEOWNERS` who can approve such changes).

I'm also adding a step to the `sycl-nightly.yml` workflow to ensure that
those copies in trunk match the release branch. That would be handy if
we were to cherry-pick some changes that add new symbols to the ongoing
release.

Author: aelovikov-intel

.github/CODEOWNERS

@@ -226,3 +226,4 @@ sycl/test-e2e/ThreadSanitizer/ @intel/dpcpp-sanitizers-review
 
 # ABI compatibility
 devops/compat_ci_exclude.sycl-rel-** @gmlueck @xtian-github
+sycl/test/abi/*sycl-rel*.dump @AlexeySachkov @KornevNikita

.github/workflows/sycl-nightly.yml

@@ -8,6 +8,21 @@ on:
 permissions: read-all
 
 jobs:
+  check_abi_symbols:
+    name: Check ABI symbols tests match release branch
+    runs-on: [Linux, build]
+    if: github.repository == 'intel/llvm'
+    container: ghcr.io/intel/llvm/ubuntu2404_build
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        sparse-checkout: |
+          sycl/test/abi
+    - run: |
+        git fetch --depth=1 origin sycl-rel-6_3
+        git diff --exit-code -I "^# RUN" origin/sycl-rel-6_3:sycl/test/abi/sycl_symbols_linux.dump sycl/test/abi/sycl_symbols_linux-sycl-rel-6_3.dump
+        git diff --exit-code -I "^# RUN" origin/sycl-rel-6_3:sycl/test/abi/sycl_symbols_windows.dump sycl/test/abi/sycl_symbols_windows-sycl-rel-6_3.dump
+
   ubuntu2204_build:
     if: github.repository == 'intel/llvm'
     uses: ./.github/workflows/sycl-linux-build.yml