[Java] Dynamic logging

[vyazelenko]

This PR adds scripts that allow enabling and disabling Agent-based logging of Aeron components.

The general form of the command is:

dynamic-logging <pid> <command> [config files...]

where <pid> is the JVM process ID and <command> is either start or stop. One can also pass an optional list of config property files or use JVM_OPTS env var instead.

Here is an example of enabling logging for the admin events of media driver process 1111 on Linux:

JVM_OPTS="-Daeron.event.log=admin" ./dynamic-logging 1111 start

And on Windows:

set "JVM_OPTS=-Daeron.event.log=admin" && dynamic-logging 1111 start

By default the log will be written to the stdout of the target process. Logging to a file can be specified via the aeron.event.log.filename property.