In the previous commit which introduced the new context failure threshold
support in the TestContext framework, the context failure tracking was
tied to an instance of DefaultCacheAwareContextLoaderDelegate.
Consequently, the feature was only supported within a given test class.
This commit therefore moves context failure tracking to the ContextCache
SPI (and DefaultContextCache) so that the feature applies to all test
classes within the current test suite (i.e., JVM).
This commit also includes the total failure count in the statistics
logged by the DefaultContextCache.
See gh-14182
f6045e8e11