Warm the settings redactor's patterns before their first timed match (#4348)

[erikdarlingdata]

Refs #4348.

The settings redactor's patterns are built with RegexOptions.Compiled and matched under a 100 ms timeout. A compiled pattern's match methods are JIT-compiled on first use. On a busy CI runner, that first-use cost could land inside the first timed match. A short, ordinary value was then masked whole, as if its match had timed out. This showed up once in CI on one of the redactor corpus tests.

What changes

• PgSettingRedactor's static constructor warms every pattern once, before any real call, on a placeholder sample that reaches each pattern's match step. A timeout during the warm-up is ignored.
• WarmedUp records that the warm-up ran. Output is unchanged.

Tests

• Warmup_RanBeforeFirstRealCall_AndShortValueIsNotMaskedWhole: the warm-up ran before the first call returns, and a short value is redacted normally.
• WarmupSampleMatches: every warmed pattern actually matches the sample, so each one's match step runs during the warm-up.
• The existing corpus, frozen-parity and forced-timeout tests are unchanged.

CHANGELOG entry

SECTION: Fixed
ENTRY:

• The settings redactor no longer masks a short value whole on its first call ([Warm the settings redactor's patterns before their first timed match (#4348) #4408]) - its patterns are warmed once at start-up, so a first-use compile cost can't count against the match time bound.
  REF:
  [Warm the settings redactor's patterns before their first timed match (#4348) #4408]: Warm the settings redactor's patterns before their first timed match (#4348) #4408