Introduce a way of finding a Ruby interpreter path without using shell

[ono-max]

Currently, we use a shell to find a Ruby interpreter path. However, this causes a lot of problems. To solve this problem, we plan to introduce a way of finding a Ruby interpreter without using a shell.

https://github.com/ono-max/vscode-ruby-interpreter-locator is a prototype.

[stellarpower]

My default shell is fish, so, the command line the extension creates doesn't execute successfully:

# /usr/bin/fish -lic rdbg --command --open --stop-at-load -- ruby /tmp/r.rb
/usr/bin/fish: unrecognized option '--stop-at-load'