AEM_CNTRL: Enhance aem_cntrl to support additional actions such as `start`, `stop`, and `waitfor`

Add additional actions to the aem_cntrl utility, such as:

`start` - This will start AEM and wait for it to be up before returning. This is useful when to automate the launching of AEM before deploying files to is from script.

`stop` - This will stop AEM and wait for it to shutdown before returning. This is useful when automating the shutdown of AEM before starting it again.

`waitfor` - Wait for a line in the log that matches the regular expression provided. This is useful for scripts that want to wait until a certain event happens (e.g. a bundle is installed, or package is finished installing).

Sub-issues to this issue will be created for the implementation of each command.

Look at the existing aem_cntrl utility code to understand its structure and how actions are implemented. The new actions 'start', 'stop', and 'waitfor' will likely involve adding new command handlers, interacting with AEM processes, and parsing log files. Check for any existing tests to see how to add new ones. Start by running the current utility to see its behavior, then extend it with the new commands.

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