Support @⁠CacheConfig("myCache") declarations for simplified config

The @⁠CacheConfig section of the reference manual provides an example
that declares @⁠CacheConfig("books").

However, unlike the @⁠Cacheable, @⁠CachePut, and @⁠CacheEvict
annotations, @⁠CacheConfig currently does not have a `value` alias for
the `cacheNames` attribute. Thus, the example in the reference manual
does not compile, and @⁠CacheConfig(cacheNames = "books") would be the
supported way to declare that.

The driving factor for this commit is therefore to provide a simplified
and consistent programming model for users that only need to define
default cache names at the type level (like in the existing example in
the reference manual).

To address that, this commit introduces a `value` alias for
`cacheNames` in @⁠CacheConfig.

See gh-35096
Closes gh-35152

(cherry picked from commit 6091453feb)

spring-context-support/src/test/java/org/springframework/cache/caffeine/CaffeineReactiveCachingTests.java

@@ -129,7 +129,7 @@ class CaffeineReactiveCachingTests {
 	}
 
 
-	@CacheConfig(cacheNames = "first")
+	@CacheConfig("first")
 	static class ReactiveCacheableService {
 
 		private final AtomicLong counter = new AtomicLong();