[FR] Make rules/ directory configurable

[rw-access]

related to #3298

Is your feature request related to a problem? Please describe.
If we could make the rules/ directory we could make this repository much more configurable, and allow our users and contributors to build their own set of rules, without having to deal with a messy fork. Instead, you could point python -m detection_rules at your own folder, which would contain a config, version lock and all of the TOML rules

Describe the solution you'd like
An environment variable is a good start, something like DETECTION_RULES_DIR=~/MyRules.toml. And we can move the version lock, packages.yml, etc. all inside that folder.

Describe alternatives you've considered

Additional context
Feature request for Git synchronization, which motivated this use case #362. When synchronizing, you could simply point to your own directory and everything would just magically sync from local <--> Kibana. We can detect conflicts as well.

[botelastic]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[botelastic]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[botelastic]

This has been closed due to inactivity. If you feel this is an error, please re-open and include a justifying comment.

[botelastic]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[botelastic]

This has been closed due to inactivity. If you feel this is an error, please re-open and include a justifying comment.

[Mikaayenson]

One approach we discussed was updating relative paths to a central config file within rulelib and importing the config file from rulelib in detection/endpoint rules repos to override any shared config params. This would cover the DETECTION_RULES_DIR use case.

[brokensound77]

This was completed in #3407 - however, since it remains in a feature branch during testing, we can leave the issue open until merged to main (or deemed as not viable)

[botelastic]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[botelastic]

This has been closed due to inactivity. If you feel this is an error, please re-open and include a justifying comment.