fix: replace removed libgl1-mesa-glx in tensorflow integration test (#2914)
* fix: replace removed libgl1-mesa-glx with libgl1 in tensorflow test
libgl1-mesa-glx was dropped from Ubuntu repos, causing flappy apt-get
failures (exit 100) in the tensorflow integration test when Docker
layer cache misses hit a mirror that no longer serves it.
* chore: replace libgl1-mesa-glx with libgl1 across codebase
Update remaining references in tests, init template, README, and
docs to use the modern package name.