LSP: Refactor definition to be similar to hover feature

[jansul]

Unfortunately it's a little hard to see the actual change in this PR between all the red and green, so hopefully some description helps.

After understanding how the hover implementation works a little better, I've refactored the definition code to be more in line with it.

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The biggest change is that I have reverted which nodes we track (see track: false everywhere), so we are no longer tracking more specific nodes such as component names etc

Instead, there is a new method cursor_intersects? which can be used to check if a node is currently being hovered over. We can use this to exit early when trying to find the definition for a "higher level" node.

e.g.

def definition(node : Ast::HtmlComponent, server : Server, workspace : Workspace, stack : Array(Ast::Node))
  
  # We are not hovering over the component name, so don't bother looking for the definition
  return unless cursor_intersects?(node.component)

  # ...
end

This removes the need for StackReader, as that was mostly used to find the reverse ("higher level" nodes from more specific ones)

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I've implemented some more of the easier "Go to Definitions" (for a separate PR for ease of review!) and it doesn't seem any more difficult to implement using this method.

[Sija]

Looks awesome 🚀