[clang] [flang] [llvm] [clang][flang][OpenMP] Fix context selector matching and scoring (PR #224431)

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MattPD wrote:

The description still implies that direct and selected TARGET forms select different variants for loop bounds, although both forms select the same variant at 9d79b83. Could it name only the host-evaluated operands whose variant selection still differs: `num_teams` and `thread_limit` of TEAMS, and `num_threads` of PARALLEL?

https://github.com/llvm/llvm-project/pull/224431