Update pSettings logic so that pSettings is mutable

[yohjimane]

Is your feature request related to a problem? Please describe.
pSettings could be made mutable, so we have access to write methods on engine side. We can build better user interfaces with this, especially for modders. Here is one specific usecase:

In this example, a modder wants to update hud positions for each weapon. Here's what the workflow for that looks like:

• Open game, launch hud tuner
• Update to desired position
• If running the game from visual studio, updated positions are accessible via console logs
• If running the game normally, open log file, or refresh it to be able to copy the updated position.
• Open specific weapon section .ltx
• Paste updated position into field
• Save specific weapon section .ltx

This entire process could be reduced to the first 2 steps, if we could write to the weapon ltx section programmatically after the position is updated.

Describe the solution you'd like
update pSettings so that it's mutable and write functions can be called.

Additional context
It looks like ShokerMod may have implemented this a long time ago, this solution could be looked at as reference:
ShokerStlk@e884cf8

[yohjimane]

I checked out the shokermod implementation, and it's not ideal because it saves every single line to the system.ltx file. Ideally, the existing file structure should stay intact.