Extension compiler pass

Move all related stuff to DIC configuration into compilers ; basically, here what was done :

- Ensured that a `broker` (or `channel_factory` ? There are some naming issue I guess) can be declared as one if it has a `swarrot.broker` tag.
- Ensured that the PECL broker is not the only one used when building commands

Missing tests though, I expect it to fail. Just wanted to throw a POC on that.