cln-plugin: make it more universally useable + tests + CI

[daywalker90]

Hi, interesting project you have here. I saw that you had no tests for you cln-plugin and since i'm a cln plugin dev myself i thought i'd help you get started on that. This PR contains:

• Some fixes to make the plugin less dependable on hard coded stuff like the log file paths, the python env path
• Removed the need to pass in the rpc path, we can get it from the plugin
• I added the execution bit to the plugin file so not everyone has to do it again
• Also replaced all print's with plugin.log since print should not be used in cln plugins (or atleast you should not write non json-rpc line to stdout)
• Boolean options can be passed in as str or bool so i handled both cases
• Added a basic startup test that runs the check_stables function once (i've added a dev_check_stables rpc method to the plugin for this) and triggers the handle_coin_movement event
• Added CI that will run the tests for the cln plugin on every PR and on commits to main (you can test more cln versions by copying main_v24.02.yml and editing the versions)

[toneloc]

This is super awesome, definitely the first substantial external contributions to this project. Thank you so much.

[toneloc]

Looks great.