fix(server/player): move health init into OnPlayerLoaded to prevent being dead in spawn selection

[iloomilo]

Description

This PR removes the health initialization from the CreatePlayer() function.
With a dedicated spawn resource, setting health here is unnecessary and may cause players to spawn dead during selection if their saved health metadata is 0.

It should also address this and related issues but I didn't test it directly for qbx_medical, just encountered a similar issue while developing my own medical resource:
Fixes Qbox-project/qbx_medical#115

Checklist

• I have personally loaded this code into an updated Qbox project and checked all of its functionality.
• My pull request fits the contribution guidelines & code conventions.

[iloomilo]

I’ve rethought this and committed a better solution. The initialization now stays within qbx_core, so there’s no need to modify the spawn resource. Optionally, initialization can be disabled in the server config