[CI] Update release_tests_binaries Dockerfile to hardcode base image tag (#20393)

Before this PR:
https://github.com/intel/llvm/actions/runs/18595720667/job/53022842454?pr=20391
After this PR:
https://github.com/intel/llvm/actions/runs/18595720667/job/53040472511?pr=20391

This PR fixes the following test failures:
```
Failed Tests (2):
  SYCL :: Matrix/SG32/joint_matrix_bfloat16.cpp
********************
Unexpectedly Passed Tests (2):
  SYCL :: Matrix/joint_matrix_bfloat16_accumulator.cpp
  SYCL :: Matrix/joint_matrix_half_accumulator.cpp
```

Hardcoding image tag helps stabilizing igc driver and prevents E2E tests
from failing on sycl-rel 6.3 compat testing, when sycl-rel docker image
is re-build

---------

Co-authored-by: Andrei Elovikov <[email protected]>

Author: uditagarwal97

devops/containers/release_tests_binaries.Dockerfile

@@ -1,7 +1,10 @@
-ARG base_tag=alldeps
+# Freeze base image to avoid using newer GPU RT/IGC when updating 
+# the image due to changes in the release branch.
+ARG base_tag=1dcf3fd93f3c13b21e9931372fe405493f7e5a7bd5ba1fca192dece74f9b9188
 ARG base_image=ghcr.io/intel/llvm/ubuntu2404_intel_drivers
 
-FROM $base_image:$base_tag
+# Remove @sha256 if replacing hash with label in base_tag
+FROM $base_image@sha256:$base_tag
 
 # Actual CI maps volumes via something like "/runner/host/path":"/__w/", so
 # these won't be visible there. They can be used when manually reproducing