CI: per-test Lite timings as an artifact, and temporary cap guards while #5208 is open

[erikdarlingdata]

Part of #5208. Lite.Tests on the hosted Windows runners has grown from about 9½ minutes of test time to about 45 in five days (+7 min/day, with only ~110 tests added). Last night's nightly was cancelled at its 90-minute build cap during the unsharded Lite run, so no release was published. This PR doesn't fix the slowdown. It makes the slowdown measurable, and keeps CI and the nightly from failing on it while it's found.

What changes

• Per-test timings: every Lite.Tests run in CI now writes an xUnit v3 result file (-xml) with per-test durations, uploaded as an artifact kept for 7 days:
  • each lite-tests shard: lite-tests-timing-<shard>, one file per chunk;
  • the nightly's unsharded run: lite-tests-timing-nightly;
  • the release-only pass in build.yml: lite-tests-timing-release.
  • The run commands are otherwise unchanged. The sharding is unchanged, and so is the release's single unsharded pass, which PR CI wall time: shard Lite tests by class-name hash, measure the PG job's ladder cost before prebuilding, and un-invert the whole-tree guards filter #3887 keeps on purpose.
• A summary in the log: .github/scripts/lite-timing-top.py prints the 25 slowest classes, by summed test time, and the 25 slowest tests, right after each run.
  • The step and the upload are if: always() and continue-on-error: true, so they can never turn a job red.
  • A missing file only means a missing artifact.
• Two temporary guards, each commented as a guard against timeout reds, not a fix, to be brought back down when Lite.Tests on hosted Windows runners grew from ~9½ to ~45 minutes in five days; the unsharded nightly run now exceeds its 90-minute cap #5208 is fixed:
  • lite-tests: timeout-minutes 20 → 30. The slowest shard reached 19 minutes on Oct 5.
  • The nightly build job: 90 → 150. Its Lite step took 45, then 64, then more than 89 minutes on three consecutive nights.
  • The release path: its job has no timeout-minutes (the 360-minute default), so it's unchanged.

Checked

• The -xml <file> option: confirmed on xunit.v3 4.0.1's in-process runner on Windows 11. A one-class run wrote a schema-version-3 results file.
• The summarizer was checked against a sample results file.
• The workflow-text pins pass on Windows: CiShardCommandLineBudgetTests (the per-chunk command-line budget), NightlyVersionInjectionTests, LockedModeRestoreCoverageTests, DarlingPathFilterGateTests and the other classes that read these files. Darling 205/0, Lite 79/0.
• Both workflows parse (actionlint and PyYAML).

SECTION: None (CI only)