`RuleLoader` cleanup and optimizations

## Overview

The purpose of this is to identify opportunities to clean up the code that makes up the rule loader (`Rule`, `rule_validator`s, etc.). Loading the rules has gotten significantly slower and while some of it is due to the necessity of expanding validation, this should explore opportunities for optimization.

rule loader profiling


## Observations

- [ ] `data` in https://github.com/elastic/detection-rules/blob/66359012c32980596473e4ace3ae73dbad89b52d/detection_rules/rule_validators.py#L251 is unused
- [ ] cache the `Version.parse` instead of parsing for every rule https://github.com/elastic/detection-rules/blob/66359012c32980596473e4ace3ae73dbad89b52d/detection_rules/rule.py#L356
- [ ] make these global constants https://github.com/elastic/detection-rules/blob/66359012c32980596473e4ace3ae73dbad89b52d/detection_rules/rule.py#L491-L492
- [ ] turn these into `cached_property` like `QueryRuleData` https://github.com/elastic/detection-rules/blob/66359012c32980596473e4ace3ae73dbad89b52d/detection_rules/rule.py#L489-L490
- [ ]

Start by reading the referenced sections of detection_rules/rule_validators.py and detection_rules/rule.py, then review the rule-loader profiling data. Compare the listed cleanup and caching opportunities against current rule-loading behavior; done means the selected optimizations are implemented and their effect on loading performance is demonstrated without changing validation behavior.

Written by the indexing model from the issue text.