Add static factory methods to RequestMatcher implementations

[marcusdacoregio]

With this PR merged, the DSL methods that create an AntPathRequestMatcher or a RegexRequestMatcher are deprecated. Instead, folks have to specify the actual RequestMatcher implementation that they want, something like .requestMatcher(new AntPathRequestMatcher("/path")).

We should add a static factory method to the RequestMatcher implementations to make it easier to create instances of the matchers, something like:

.requestMatcher(AntPathRequestMatcher.fromPattern("/path"));