Frontier build update

[nkoukpaizan]

Merge request type

• New feature
• Resolves bug
• Documentation
• Other

Relates to

• OPFLOW
• SOPFLOW
• SCOPFLOW
• TCOPFLOW
• CMake build system
• Spack configuration
• Manual
• Web docs
• Other

This MR updates

• Header files
• Source code
• CMake build system
• Spack configuration
• Web docs
• Manual
• Other

Summary

• This updates the Spack configuration on Frontier to use ROCm 6.3.1.
• This also removes buildsystem setup for decommissioned OCLF computers (Ascent and Summit).
• Deactivating PNNL mirror.
• Updating GH actions.

[pelesh]

Built ExaGO from scratch without any problems. All but one test pass. The failing test is for experimental ExaGO code and the failure is unrelated to this PR.

59/59 Test #59: Python_pytest_MPI ............................................................   Passed    3.21 sec

98% tests passed, 1 tests failed out of 59

Label Time Summary:
incline-skip    =  60.96 sec*proc (2 tests)

Total Test time (real) = 336.95 sec

The following tests FAILED:
	 19 - FUNCTIONALITY_TEST_OPFLOW_RAJAHIOP_SPARSE_GPU_TOML_TESTSUITE (Failed)

I suggest we merge.

[abhyshr]

This mostly touches the buildsystem files so looks good to merge.

[nkoukpaizan]

This mostly touches the buildsystem files so looks good to merge.

I don't have the authorizations to merge this myself. Someone who does will have to merge.