* Eliminate duplicates in Helix `TestRunner`
- do not add source that's already in NuGet.config
- configuration file now part of Helix content
- do not re-set an env variable that's set in `runtests.*`
nit: simplify `%Path% setting in runtests.cmd
- always quote the value
- but, keep the `SETLOCAL` command
- don't pollute environment on Helix agents
* Remove `--source` options we don't need anymore from `runtests.*`
- nit: add `--no-restore` to `dotnet run` command after `dotnet restore`
* Add `--arch arm64` to ARM64 `restore` build steps
- #25397
- was restoring for the wrong architecture
nit: add `--no-restore` to Helix project build steps
- already restored
12f92dbc8c