Add code lens extension (for Rails tests)

[adisonlampert]

⚠️ Must be merged after Shopify/ruby-lsp#666

Description

Add code lens extension to recognize Rails tests:

test "should test something" do
    # assert something
end

A Rails test is a SyntaxTree::Command with the test name as the first argument so the extension implements on_command to create code lenses for Rails tests.

Shopify/ruby-lsp#666 adds parameters to initialize so I also updated the hover extension + tests.

Testing

Created code_lens_test.rb that checks that Rails-styled tests are recognized and a CodeLens response is created.

You can also manually test by checking out this branch and running the tests in code_lens_test.rb from the file.

• Note: Until Make CodeLens a Listener ruby-lsp#666 is merged, you must make sure the ruby-lsp gem is installed from this branch

[andyw8]

I have continued this in #67 - I'm leaving this as-is to allow for a comparison.