Build test items in hierarchy if it's supported

[st0012]

Motivation

Currently, tests in Test Explorer are assumed to only have 2 levels, which is incorrect, especially with RSpec tests.

With a 2 level nesting test file:

class ParentTest < Minitest::Test
  def test_foo; end

  class FirstChildTest < Minitest::Test
    def test_bar; end
  end

  class SecondChildTest < Minitest::Test
    def test_baz; end
  end

  def test_foobarbaz; end
end

The current implementation doesn't display the nesting nor group tests correctly:

But with Shopify/ruby-lsp#1214 and this PR, we can deliever the correct result:

Closes Shopify/ruby-lsp#1744

Implementation

• If code lens items has group_id data attribute, we can build items hierarchy with them.
• Otherwise, fallback to the current approach.

Automated Tests

Manual Tests

[st0012]

I feel blending the 2 versions of implementation together makes things harder to understand and also harder to remove the fallback. So I want to separate them with simple if/else condition and simply remove the fallback when we're ready to do so.

[vinistock]

Very clean, the implementation looks good to me. Do you have a project that we can manually test this on? Does IRB use nested test declarations?

[st0012]

The only minitest/test-unit file that I have to test against is this.

Before (incorrect nesting)

After