This commit adds auto-configuration and documentation for MockMvcTester,
a wrapper of MockMvc that provides AssertJ integration as well as a
fluent API to build requests. The main differences compared to the
regular MockMvc are as follows:
* No need for static imports for building requests and define assertions
* No need to handle unchecked exception as they can be asserted instead
* Support for converting the response body to data types
Closes gh-41198
e5859aedaf