Prior to this commit, `WebMvcTags' would always mark as "NOT_FOUND" or
"REDIRECTION" *any* exchange with responses of 404 and 3xx status, even
if those responses are actually returned by Controller handlers.

This commit checks inverts those checks and first considers if the
"BEST_MATCHING_PATTERN_ATTRIBUTE" request attribute is present and uses
it - then falls back to "NOT_FOUND" and "REDIRECTION" to avoid
cardinality explosion.

Fixes gh-12577