Merge #7799

7799: Related tests r=matklad a=vsrs

![tests](https://user-images.githubusercontent.com/62505555/109397453-a9013680-7947-11eb-8b11-ac03079f7645.gif)
This adds an ability to look for tests for the item under the cursor: function, constant, data type, etc

The LSP part is bound to change. But the feature itself already works and I'm looking for a feedback :)



Co-authored-by: vsrs <vit@conrlab.com>

editors/code/src/main.ts

@@ -113,6 +113,7 @@ async function tryActivate(context: vscode.ExtensionContext) {
     ctx.registerCommand('newDebugConfig', commands.newDebugConfig);
     ctx.registerCommand('openDocs', commands.openDocs);
     ctx.registerCommand('openCargoToml', commands.openCargoToml);
+    ctx.registerCommand('peekTests', commands.peekTests);
 
     defaultOnEnter.dispose();
     ctx.registerCommand('onEnter', commands.onEnter);