Support `InputStream` as a source of `RequestBody`

**Is your feature request related to a problem? Please describe.**
Currently `RequestBody` can only be constructed from `ByteBuffer`. If a caller wants to supply data from an `InputStream` this API forces an allocation and copy of the data in the stream into an intermediate buffer.

**Describe the solution you'd like**
I would like to be able to create `RequestBody` from an `InputStream`. It seems that `mark` and `reset` functionality can be used to implement rewinding in `RewindableContent`.

**Describe alternatives you've considered**
I can use an intermediate buffer solution and it works but it's not ideal.

Comienza localizando la API de construcción de RequestBody y la implementación de RewindableContent; después, compara cómo se gestiona la fuente ByteBuffer existente. Determina el comportamiento requerido de mark/reset para un InputStream y verifica que la nueva fuente evite la copia intermedia sin dejar de ser rewindable.

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