Add support for MsgPack

[AmirQSD]

I had to alter a few tests that included base64 decode, since with messagepack, binary data is sent as bytes, without the need to specify the base64 encoding.

[qsdstefan]

Looks good for now, but you will need to update .github/workflows/check.yml by adding protocol: [ 'json', 'msgpack' ] to the matrix, then under env you should pass PROTOCOL as PROTOCOL: ${{ matrix.protocol }} to provide the environment variable in the final workflow step which is Run test suite
See check.yml#L14 for details

[qsdstefan]

As previously stated, update .github/workflows/check.yml to run tests for binary protocol version.

[owenpearson]

Really nice work 🙂

Couple of formatting fixes to be made, my main comment however is that according to RSC8a msgpack should be the default as long as PHP as a platform has sufficient support for it. I haven't looked at rybakit/msgpack but are you able to comment on whether it should work fine for any PHP application (ie does it require any system dependencies that weren't already required by ably-php)? If it's not gonna be a breaking change then I think we should change the default useBinaryProtocol client option to true.

[qsdstefan]

Looks good after the changes to make MsgPack the default.

[owenpearson]

LGTM, thanks 👍

[sacOO7]

Other than few changes, looks good to me overall 👍

[sacOO7]

Lgtm