Feat: Add "Definition" Support for for template Entries

[Stuart-Wilcox]

Motivation

My teams makes significant use of the ADO Pipeline template paradigm and has many template references all over our pipeline definitions.

One of the most annoying things about this pattern is that when navigating around in VSCode, you need to select the full template path, copy it, and CTRL+P to open it in a new tab. Thus the motivation here is to have a seamless experience like in JS/TS where using F12 (or context clicking and selecting "Go To Definition") which takes you right to the template locally.

Implementation

• added definitionProvider to the capabilities so this option will show on the menu and otherwise be available
• followed the paradigm of hover but with some modifications for the definition use case
  • when the definition flow is invoked, only template items will work
  • additionally, only non-suffixed templates, or templates suffixed with @self will work
• support relative & abs (from workspace root) template paths
• opens the template on the first line in first position

[JulienDesalliers]

That's awesome, I've been wanting something similar for a while now!

[50Wliu]

Okay, played around with it a bit and pushed some of my changes to get things working. Notably:

• Only go-to-definition on the value of the template (before, you could also try ctrl+clicking the literal template word which would fail).
• Get the URI stuff figured out. Location.create wants a URI in the form of a string, so toString() was the right call after all. Sorry for the doubt here! It was tricky to figure out without the type signatures :P
• Fix the absolute pathing so that it works cross-platform. Most of this was normalizing separators to whatever the current platform separator is, though I also needed to tweak server.ts so that it stopped trying to parse a URI from a very-deprecated rootPath. Now it parses from a still-deprecated-but-slightly-less-so rootUri! (We really need to sync this repo with the last 5 years' worth of changes from upstream...)

@Stuart-Wilcox if these changes look good to you, I'll push the big green button :).

[Stuart-Wilcox]

Thanks for adding those changes, it all looks good to me!

[50Wliu]

Thank you for the contribution!!