std.regex: drop redundant bmatch run from the test suite

[kubo39]

Rationale

match and bmatch are equivalent (both pick the engine from the pattern), so running run_tests!match() only.

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• I have performed a self-review of my code.
• [ ] If my PR fixes a bug or introduces a new feature, I have added thorough tests.
• [ ] If my changes are non-trivial and do not concern a reported issue, I have added a changelog entry.

[DmitryOlshansky]

Since engines are picked from pattern it makes it truly important to run all engines in test suit. So just dropping bmatch is not a good solution, what is needed is a way to pick engine at least internally.

[kubo39]

At first I thought, but since that pattern — explicitly forcing the backtracking engine — can't be reached through the public API, I wonder if it's worth it.

[DmitryOlshansky]

It's not public but the engine better be tested even if currently it is not selected for the pattern.

[thewilsonator]

It wold seem to me the solution here is (potentially via a private API) to force the engine irrespective of the pattern, and then test all of the engines on whatever the set of patterns comprise the test suite.

[kubo39]

Okay, I'll add the internal helper later.