This commit adds the necessary infrastructure for the support of HTTP
Range requests. The new `ResourceRegionEncoder` can write
`ResourceRegion` objects as streams of bytes.
The `ResourceRegionEncoder` relies on an encoding hint
`BOUNDARY_STRING_HINT`. If present, the encoder infers that multiple
`ResourceRegion`s should be encoded and that the provided boundary
String should be used to separate ranges by mime boundaries.
If that hint is absent, only a single resource region is encoded.
Issue: SPR-14664
55d6f88dcd