Prior to this commit, the `ResourceHttpMessageConverter` would support
all HTTP Range requests and `MethodProcessors` would "wrap" controller
handler return values with a `HttpRangeResource` to support that use
case in Controllers.
This commit refactors that support in several ways:
* a new ResourceRegion class has been introduced
* a new, separate, ResourceRegionHttpMessageConverter handles the HTTP
range use cases when serving static resources with the
ResourceHttpRequestHandler
* the support of HTTP range requests on Controller handlers has been
removed until a better solution is found
Issue: SPR-14221, SPR-13834
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