Introduce `value` alias for `cacheNames` in `@CacheConfig`

[sbrannen]

#35096 made me aware of the fact that @CacheConfig does not have a value attribute alias for cacheNames, even though the rest of the cache-related annotations (such as @Cacheable, @CachePut, etc.) do have a value / cacheNames alias pair.

Thus, we should introduce a value alias for cacheNames in @CacheConfig as well.

[snicoll]

@sbrannen the lack of alias is intentional and I don't think the analogy with the other annotations is correct. We wanted cacheNames to be explicit as it's not about a cache operation but configuration of the infrastructure.

[sbrannen]

Reopening to backport to 6.2.x.