Implement std::hash for Str::StringRef
Add framework/Resource and use it for audio/Sample

This is somewhat WIP, there are a few blocking TODOs,
especially the one near the declaration of Manger::Register
Add the S_{Begin/End}Registration syscalls and use them in cgame
Resource: introduce a Handle WIP for c&c
Fix compilation of std::hash<Str::StringRef>
Fix a stupid 'optimization' in std::hash<Str::StringRef>
Update the doc of Resources for Handles
Cleanup adding bot obstacles for buildings.
Half human build delay timer.
Set initial buildable health to 25%.
Remove (Advanced) Basilisk and Advanced Dretch. Add a basic implementation of Mantis.

Mantis has low health and a mediocre claw attack. It is fast and has the
ability to do quick forward pounces (copied from the Advanced Dretch).
Mantis health 50 → 75. Wallpounce cooldown 750 → 1000.
Make the Mantis slower but give its primary attack a slowing and stamina draining effect.

Mantis speed: 1.3 → 1.25, Slow time: 1s, Slow modifier: 0.75, Total stamina
lost while slowed: 20%.
Don't penalize Mantis pounce when moving up a slope.
Make AI use the Mantis pounce.
Move stamina usage, restoration and loss into a single synchronized function.
Make Mantis slow actually work.
Fix a potential loop.
Remove unused variables in ClientTimerActions.
Set both team's build delay to 60% of build time.