Add cvar for stamina restoration speed based on fps reference.

[Garey27]

This PR fixes time to restore stamina after jump based on reference fps.

Which described on another PR:
#755

After setting cvar mp_stamina_restore_rate to “100.0”, players with no matter how high (1000) or low (30) fps will have the same stamina recovery rate after a jump as they would have with 100 fps.

[Vaqtincha]

ifdef REGAMEDLL_ADD forget ?

[AlexSwartz]

Hello, I test this fix and there is some glitch when client FPS is greater than ~145FPS. When landing, there is a slight judder to the camera.

I tested with mp_stamina_restore_rate 100, with this merged to the latest release 5.26.0.668.

https://streamable.com/azz0gy

Edit:

Slow motion of the judder on landing with 500 fps:
https://streamable.com/icvrek

As FPS increases, the duration of the judder increases. I have measured the judder in slow motion and counted how long the judder lasts upon landing:

275FPS = judder duration 473ms
500FPS = judder duration 571ms
1000FPS = judder duration 624ms

[Garey27]

@AlexSwartz This because client predict your movement with original PM_Move code. (In Valve's client.dll library), and when server send you SVC_CLIENTDATA, client try to synchronize it to server's one, ideally all fixes in pm_* code should be replicated in client library.