feat(core/rdr3): block level loading

[Ehbw]

Goal of this PR

Block Level/Game loading once INIT_CORE has been fully loaded. This matches the behaviour on FiveM while also enabling functionality for replace_level_meta in RedM.

How is this PR achieving the goal

By preventing game loading post INIT_CORE until g_callBeforeLoad (set in RageGameInit::LoadGameFirstLaunch returns true on server connection or sp load)

This PR applies to the following area(s)

RedM

Successfully tested on

Game builds: 1436, 1491

Platforms: Windows

Checklist

• [x] Code compiles and has been tested successfully.
• [x] Code explains itself well and/or is documented.
• [x] My commit message explains what the changes do and what they are for.
• [x] No extra compilation warnings are added by these changes.

Fixes issues

https://forum.cfx.re/t/replace-level-meta/4797157