* Tweaks to make dotnet-watch run faster
* Previously dotnet-watch calculated the watch file list on every run by invoking MSBuild. This
changes the tool to only calculate it if an MSBuild file (.targets, .props, .csproj etc) file changed
* For dotnet watch run and dotnet watch test command, use --no-restore if changed file is not an MSBuild file.
* Add opt-out switch
* Update src/Tools/dotnet-watch/README.md
* Fixup typo
* Update src/Tools/dotnet-watch/README.md