Refine `MimeMappings` so that common default mappings are included
by default and the complete set is only loaded when needed.
The `TomcatServletWebServerFactory` has been updated so that if
`TomcatEmbeddedContext` is in use the mime mapping are used
directly rather than being copied to another Map.
The `AbstractServletWebServerFactory` class has also been changed
to use a lazy copy of the mappings. This should mean that the
complete set of properties is only loaded if the user mutates
the mappings.
See gh-32101
86f38e15f0