Bound the settings redactor's matching time (#4348)

[erikdarlingdata]

Refs #4348.

• Every pattern in PgSettingRedactor has a bounded matching time. The one pattern with no lookarounds or backreferences uses RegexOptions.NonBacktracking. The others carry a 100 ms match timeout.
• If any pattern times out, the whole value is masked. The warning names only the setting.
• The three name-matching patterns anchor at a name boundary and check for their separator with a linear lookahead first, so a long name run with no separator costs linear time. The output is unchanged.

Tests

• Long-input timing: 3,200 and 32,000 characters, with and without a trailing assignment. Each finishes under 50 ms after a warm-up run; measured locally at under 10 ms, up to 100,000 characters.
• A forced timeout, through a test-only, per-flow timeout seam: the whole value is masked, and the warning names only the setting. A callback that throws doesn't escape.
• A frozen parity list: 39 crafted inputs whose expected output was captured from the previous redactor.

CHANGELOG entry

SECTION: Fixed
ENTRY:

• The PostgreSQL settings redactor has a bounded matching time ([Bound the settings redactor's matching time (#4348) #4392]) - Each redaction pattern runs under a time bound. A value that reaches it is masked whole, and the warning names only the setting.
  REF:
  [Bound the settings redactor's matching time (#4348) #4392]: Bound the settings redactor's matching time (#4348) #4392