Soft Dependencies for Text Mesh Pro, UGUI, and the "New" Input System

[Cameron-Micka]

Overview

This PR makes Text Mesh Pro, UGUI, and the "New" Input System optional dependencies for Graphics Tools.

Note, samples still require Text Mesh pro & UGUI when displaying UGUI features.

Changes

• Fixes: Soft Dependencies for Text Mesh Pro, UGUI, and the "New" Input System #137

Verification

As a reviewer, it is possible to check out this change locally by using the following
commands (substituting {PR_ID} with the ID of this pull request):

git fetch origin pull/{PR_ID}/head:name_of_local_branch

git checkout name_of_local_branch