Should not promote TMP_Text.SetCharArray because it allocates too much

[laicasaane]

I've run some tests and TMP_Text.SetCharArray allocates too much.

Environment:

• Unity 2021.3.5f1
• API level: .NET Standard 2.1
• Use Incremental GC: on
• TextMeshPro 3.0.6
• CPU: Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
• OS: Windows 10 21H2 64bit

Test cases: https://gist.github.com/laicasaane/2b3f3abee9581db90bc21bc4905bc49b