Tighten up our compression framework.

[jpountz]

We have a compression framework that we use internally, mainly to compress some
xcontent bytes. However it is quite lenient: for instance it relies on the
assumption that detection of the compression format can only be called on either
some compressed xcontent bytes or some raw xcontent bytes, but nothing checks
this. By the way, we are misusing it in BinaryFieldMapper so that if someone
indexes a binary field which happens to have the same header as a LZF stream,
then at read time, we will try to decompress it.

It also simplifies the API by removing block compression (only streaming) and
some code duplication caused by some methods accepting a byte[] and other
methods a BytesReference.

[jpountz]

I'm reading the description again and I've probably not been clear enough about what changed:

• If you call CompressorFactory.compressor(ChannelBuffer) and the compression format is not detected, you will get an exception. This was already working this way at the call site: MessageChannelHandler.messageReceived, now it's done directly in the framework.
• If you call CompressorFactory.compressor(BytesReference) and the bytes are not either some xcontent bytes or some compressed xcontent bytes, then you will get an exception. There is no way in general to detect if some bytes are compressed because nothing prevents an arbitrary bytes reference to have the same header as a LZF block so we enforce that this method be only used on xcontent bytes, which is how we are using this method (to the notable exception of BinaryFieldMapper, which is buggy as described in the description).

[jpountz]

I opened #11280 to fix the BinaryFieldMapper issue.

[jpountz]

I pushed a new commit to also use DEFLATE (with a compression level of 3) instead of LZF. The reason is that even if LZF might be faster, we have had some issues recently like #7210 or #7468 and expect that using something that is more widely used like DEFLATE will protect us better from corruptions in the future.

[rjernst]

copy-pasted from NotCompressedException?

[rjernst]

LGTM, I left a couple minor comments.

[jpountz]

@rjernst Thanks for the review, I pushed a new commit.

[rjernst]

LGTM