dotnet format infrastructure tasks

- [ ] Change dependency load logic to pull from relative paths in the SDK
- [ ] Add new hidden commandline options to manually override where we load dependencies from
- [ ] Add tests to the SDK repo to validate that we can always format the templates that ship in the SDK
- [ ] Add similar tests in the dotnet format repo to verify the global tool works with the latest preview sdk
- [ ] Update main to target net7. Assume that the runtime we target going forward will match the sdk we ship in
- [ ] rationalize our completion api and surface are in the SDK. instead of duplicating the commands find some way to call into the real dotnet format process. If we cannot do chaining of completion processes we should just drop the feature