JCLOUDS-410. Deprecate Payload.getInput

We plan to transition Payload to ByteSource in the next major release.
Unfortunately Payload.getInput masks its checked exception and
ByteSource.getInput is final so we cannot continue to mask the
exceptions.  Deprecation of getInput and addition openStream allows us
to transition callers from the former to the latter.
JCLOUDS-410. Add support for ByteSource Payloads

Also deprecate byte[], File, InputSupplier<InputStream>, and String
Payloads.  Callers should instead provide a ByteSource via
ByteSource.wrap(byte[]) and Files.asByteSource(File)
Address Checkstyle violations