perf: dedupe getSkills(cause) in combat skill dispatch

- MobType.executeSkills was calling getSkills(cause) twice on async triggers (once sync, once inside the async lambda), allocating a fresh ConcurrentLinkedQueue both times on combat-related triggers
- Now cached once and captured by the lambda
- MobType.getSkills swaps containsKey+get for one get + null check on the SPAWN_OR_LOAD branch
- VariableRegistry uses parseInt/parseFloat/parseDouble for primitive defaults and string-value parses instead of valueOf (no box round-trip)
- MythicUtil.splitIgnoringParentheses iterates by charAt instead of allocating a char[] copy
- Same outputs; ~1.9x faster async combat skill dispatch

Build 5660

5.11.2-5622

5.11.2-5620

5.11.0-5575

5466 5.10.0

5.9.2 Build 5456

v5.9.1-5441

Build 5359

v5.8.0-SNAPSHOT/5296