[llvm-branch-commits] [CI][NFC] Refactor compute_platform_title into generate_test_report_lib (PR #166604)

[Aiden Grossman via llvm-branch-commits]

https://github.com/boomanaiden154 created https://github.com/llvm/llvm-project/pull/166604

This enables reuse in other CI components, like
premerge_advisor_explain.py.