Adapt dotnet/runtime editor config

[yuliadub]

Adapt the runtime/.editorconfig at main · dotnet/runtime (github.com) for both TES and CoA repos. Go through and correct any issues caused by the new editorconfig policies (specifically naming variables for statis and private types).

Make sure to change the HeaderText that the runtime editor config specifies to match what would make sense for our repos/licenses.

Create PRs with all the changes to be merged with least possible disruptions/large merge conflicts, so ideally this can be done where there are no large PRs that are pending to be merged.