Out-of-proc cross-runtime TaskHost should be spawned with `/nodereuse:true`

> This shouldn't pass as written--I would expect it to have `/nodereuse:true`. If it doesn't we at least need a follow-up item. 

 _Originally posted by @rainersigwald in [#12642](https://github.com/dotnet/msbuild/pull/12642/files#r2433885645)_