CLEANUP: pools: rename pool_*_{from,to}_cache() to *_local_cache()

CLEANUP: pools: rename pool_*_{from,to}_cache() to *_local_cache()

The functions were rightfully called from/to_cache when the thread-local
cache was considered as the only cache, but this is getting terribly
confusing. Let's call them from/to local_cache to make it clear that
it is not related with the shared cache.

As a side note, since pool_evict_from_cache() used not to work for a
particular pool but for all of them at once, it was renamed to
pool_evict_from_local_caches()  (plural form).