Improve ResolvableType.hashCode() for better performance

Prior to this commit, when there was a lot of entries in the
ResolvableType.cache HashMap, getting a simple value could
take a lot of time due to a lot of calls to ResolvableType.equals().
ResolvableType.equals() used this.type, getSource(),
this.variableResolver.getSource() and this.componentType, but
ResolvableType.hashCode() used only this.type.

With this commit, ResolvableType.hashCode() now uses the same
fields than ResolvableType.equals().

Performance on the spring-resolvabletype-benchmark project:
 - 8000 us before this commit
 - 120 us with this commit

Issue: SPR-12122
Update documentation

This commit updates the documentation to mention that the #result
object is available in the SpEL context for computing the key to use
for a @CachePut operation.

Issue: SPR-12125
Improve configuration changes in GuavaCacheManager

Prior to this commit, setting the parameters used to build the caches
was fragile in static mode as the caches were created right when the
setCacheNames setter was called.

This commit provides a better handling of such arguments and also
provide a way to restore the dynamic mode if necessary.

Issue: SPR-12120