Add quality of life Suhayl plugin

Summary:
Allow to reduce rain rate.

Speed up happy ghasts.

Test Plan:
Tested on server:

• no rain during quick test periods
• happy ghasts are fast
• adult happy ghasts not harmed anymore by snowballs

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D3646