The New Fluent Theme should be Fluent2

### Description

I've brought this up before but this is a last attempt to get the naming right. Once it releases I suspect we are stuck. I won't rehash fully why we should be using the official name: Fluent2, however, it's a matter of branding and versioning.

1. If the versioning is out of sync this is going to cause an issue if ever we do need a Fluent1 or a future Fluent3
2. You are violating Microsoft's own branding and naming conventions. See here:
* https://fluent2.microsoft.design/
* https://www.figma.com/community/file/836828295772957889/microsoft-fluent-2-web

For non-developers calling it Fluent is fine. But developers and designers need to be more specific.

### Reproduction Steps

N/A

### Expected behavior

Fluent2 should be the name of the new theme

### Actual behavior

Fluent without any version is the current name of the theme

### Regression?

_No response_

### Known Workarounds

Fluent Theme

### Impact

_No response_

### Configuration

_No response_

### Other information

_No response_