Code cache subtask tracking

Tracking some specific subtasks required as we progress towards fully functional code caching.

* #5116
* #5117
* #5123
* Persistently mmap caches
* Delete caches generated from old FEX versions
* Enable NOP padding only for cache generation+validation runs (see #5110)
* Debounce cache regeneration when the number of new blocks is low
* Ensure we never ever produce zero-size code maps or move to a non `flock()`-based method of guarding code map access (see #5127)
* Machine-agnostic CodeMapIds
* #5141
* CodeBuffer resizes should preserve data
* Drop CodeBuffer size limit (at least when generating caches and validating them)
* Multi-threaded cache generation (#5203)
* On-disk compression
* Cache header only allocates 8 bytes for version information
* Moving RootFS folder invalidates code maps
* `FEX_MAXINST` poisons code maps (similar to `FEX_MULTIBLOCK`)
* Consider full guest executable hashing for consistency checking of file IDs
* Consider de-virtualizing `CodeCache::ComputeCodeMapId`
* https://github.com/FEX-Emu/FEX/issues/5379