Audit run-fail ui tests to see if they need *exact* run stderr/stdout

[jieyouxu]

compiletest triage: I'm not convinced switching error-pattern run-fail ui tests to use only the current form of check-run-results is an improvement over error-pattern unconditionally. If anything, it would be a regression to flaky tests in many cases that are sensitive to exact run stdout/stderr (line numbers, backtraces that can depend on platform-specific unwind mechanism, concrete addresses, version numbers, etc.).

I would be in favor of auditing some of these run-fail tests and sparingly add check-run-results if the exact run stderr/stdout is critical for the intention of the test, but not in a blanket fashion. As such, I'm going to close this issue in favor of a more concrete audit issue.

Originally posted by @jieyouxu in #65865

[jieyouxu]

See also Audit {check-run-results, error-pattern, check-stdout, normalize-*, dont-check-compiler-*, run-rustfix, rustfix-only-machine-applicable, forbid-output} family of directives.

[jieyouxu]

E-medium because you need some experience to not accidentally make a test flaky and to know if a test needs to check for exact run stderr/stdout.