[PHO-343] Feature/new sample

[HarrisonHough]

PHO-343

Description

• This PR adds a new avatar creator sample with both an Avatar Creator scene and a third person character (game) scene.
• It also adds some new things like support for cancellation tokens in most async web requests other than that there wasn't much changed in the core part of the sdk, the rest is only sample specific scripts or assets.
  NOTE: We decided to make the sample in URP (which is default pipeline in Unity 6). So be aware that if you are testing this in other render pipelines (built in or HRDRP) you will encounter shader issues. This will be mentioned in the docs.

How to Test

Install the sdk via this url

https://github.com/readyplayerme/rpm-unity-next-gen-sdk.git#feature/newSample

When testing the main things to focus on are:

• package import
• Demo account login (via Unity Character Style Manager window
• Importing the Avatar Creator Sample
• Running the Avatar Creator sample
• Building and running the avatar creator sample on builds.

Checklist

• Tests written or updated for the changes.
• Documentation is updated.
• Changelog is updated.