perf testsuite: Add common output checking helper

As a form of validation, it is a common practice to check the outputs
of commands whether they contain expected patterns or match a certain
regular expression.

This output checking helper is designed to allow checking stderr output
of perf commands for unexpected messages, while ignoring messages that
are known to be harmless, e.g.:
  "Lowering default frequency rate to \d+\."
  "\d+ out of order events recorded."
  etc.

Signed-off-by: Veronika Molnarova <[email protected]>
Cc: Athira Rajeev <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Namhyung Kim <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Michael Petlan <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

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