Avoid inverted cache and statistics lock order

[fhgffy]

CacheStatsTracker.info() held the statistics lock while asking the cache for its length. Cache operations hold the cache lock before updating statistics, so a concurrent snapshot and get() could wait on each other indefinitely.

Read the entry count before taking the statistics lock. The regression coordinates the competing operations and bounds the test's lock waits so the failing case cannot leave hanging threads. It fails on the original code and passes with the new order.

Validation on Windows: all 118 tests and doctests pass with 100% source coverage on every supported Python version (3.10, 3.11, 3.12, 3.13, and 3.14). Ruff formatting/lint, mypy, the warning-as-error documentation build, wheel/sdist build, and twine check pass on Python 3.12.

[coveralls]

coverage: 100.0%. remained the same — fhgffy:fix-stats-lock-order-20261011 into dgilland:master