Feature Request: Allow format to select only one framework in case of multi-target projects

Migrate [#2057](https://github.com/dotnet/format/issues/2057) to SDK repo

### Is your feature request related to a problem? Please describe.
Why this feature is needed:.
When run 'dotnet format' in multi target project, there may cases where format tool can not merges the changes in multi frameworks eg net6, net472 and had to add unhelpful comments like:
```
/* Unmerged change from project 'xxxx (net6.0)'
Before:

After:

*/
```
Even worse, the unmerged change will not be logged.

See [#1634](https://github.com/dotnet/format/issues/1634)

### Describe the solution you'd like
It is great if we can avoid such problems by passing framework option in commandLine , e.g:
```
dotnet format --framework net472
```

### Additional context
This behavior makes `dotnet format` unuseable for multi-target projects.