[6.4.0 Agent Release] - Publicly document jar collector config

[jasonjkeller]

This is dependent on #183 being included in the 6.4.0 agent release and the artifact being published.

Along with this PR I think we should update the public agent config doc to include a section on the jar_collector config options:

  jar_collector:
    enabled: true # default true
    max_class_loaders: 300 # default 5000
    skip_temp_jars: true # default true
    jars_per_second: 5 # default 10

It doesn't look like we publicly document any of these config settings.

[jack-berg]

Done.

And it also turns out that max_class_loaders isn't used anywhere, so I've removed that property in a new commit on #183.