Additional updates for API versioning in test and client support

[rstoyanchev]

Some test support was added in #34568, to allow inserting a version with WebTestClient. After some more thought and use, there are more places we could update.

Make it possible to configure (server side) API versioning for mock server tests, e.g. standalone MockMvc tests, and the equivalent in WebFlux via WebTestClient#bindToController.

Support setting ApiVersionInserter in MockMvc tests via ConfigurableMockMvcBuilder, and specifying the version for a request through the RequestBuilder or MockMvcTester.

The ApiVersionInserter in the client support can also do with some updates based on actual use.