[CI] Update DCU image toolchain to GCC 12.2 (#79600)

* [CI] update DCU image toolchain to GCC 12.2

* update dcu ci runs-on group

* [CI] restore GCC 12 runtime after DTK setup

* [CI] preserve runtime paths in CTest environments

* [HIP] Fix eye and BLASLt workspace on DCU

* [CI] isolate DCU cache and diagnose analyzer SIGILL

* [CI] isolate DCU runner-specific failures

Disable AVX for DCU builds so Intel build hosts do not emit instructions unsupported by Hygon test runners. Revert the ineffective eye kernel rewrite and check the copied raw buffer before the ATen indexing path.

* [CI] trace DCU eye device buffer

* [CI] isolate DCU GCC 12 runtime libraries

* Update _Linux-DCU.yml

* [CI] restore DCU runtime paths and skip eye test

* [CI] fix distribute GCC 12 runtime path

* [CI] prioritize host CUDA driver in coverage tests

* [CI] mirror mpdecimal source in BOS

* [CI] validate GCC installation in Ubuntu 20 image

* [CI] mirror GCC 11 source in BOS

* [CI] mirror GCC 11 prerequisites in BOS

* [CI] mirror binutils source in BOS

* [CI] mirror GCC 12.1 prerequisites in BOS

* [CI] Temporarily skip Python 3.13t requirements

* [CI] Skip ATen eye test registration on DCU