Previously, Razor server discovery for the `build-server shutdown` command was
implemented by invoking MSBuild on a project file in the current directory to
evaluate the path to the Razor server dll. This was problematic since it would
only discover a single running Razor server instance and required that the user
run the `build-server shutdown` command from a specific location.
Razor's server now writes a "pid file" to a well-known location
(`~/.dotnet/pids/build`) which the command can now enumerate to discover, and
shutdown, the running Razor servers.
This commit changes the Razor server discovery to use the pid files and removes
the requirement that users need to run the command in specific directories to
work.
Fixes#9084.
1ade191cb6