Remove logstash_commons dependency

Migrated the `logstash_commons` calls to use attributes on elkstack instead. Added tests to verify the templates are pushed out successfully when converged with elkstack::agent in a wrapper recipe. If elkstack isn't present, these additional attributes simply do nothing. If elkstack is present but a particular technology is not present, logstash simply ignores log files it doesn't find.

With the additional requirement of passing attributes to elkstack, logstash_commons no longer seems like a viable community option, so I'm just going to merge it into stack_commons as well, so that logging configs live side-by-side the technologies themselves.