[FR][DAC] further decouple reliance on default rule dir locations

[brokensound77]

Note: this work will target the DAC-feature branch

related to #3407

---

These global constants:

detection-rules/detection_rules/rule_loader.py

Lines 27 to 30 in 303a64e

	DEFAULT_PREBUILT_RULES_DIR = Path(get_path("rules"))
	DEFAULT_PREBUILT_BBR_DIR = Path(get_path("rules_building_block"))
	DEFAULT_PREBUILT_DEPRECATED_DIR = DEFAULT_PREBUILT_RULES_DIR / '_deprecated'
	DEFAULT_PREBUILT_RTA_DIR = get_path("rta")

Need to be revised to fully adopt the portable approach introduced by #3407 (using RULES_CONFIG.*).

However, the use of these variables is not consistently just for rule loading, and they have several hardcoded dependencies on them, so they cannot simply be replaced.

[eric-forte-elastic]

Additional Considerations:

• This PR should make BBR rules directories optional
• In the config, we should have a separate path list for BBR rules dirs as they are handled differently
• In the config, we should also have an RTA section (expected to be optional as well)
• Need to update the current loading of rules to support a list of paths to be loaded, instead of one.
• Need to update the example config generation to match the formatting specified from the above considerations.
• Need to decide whether or not deprecated rules are optional and whether or not we should make this be a configurable directory location (as opposed to _deprecated relative to the rules directory.)

[eric-forte-elastic]

PR is merged, this issue is now complete.