Add possibility of DebugVariables navigation

[federicobozzini]

What it does

In some cases it might be useful to allow navigating DebugVariables, making it possible to understand things like what is their parent in the Debug panel or in which scope they are defined.

An example might be the theia-cpp-extension where the context of a variable is important. Another example is adding different menus on C modules if they are shown as sub-elements of a scope.

How to test

To test this some new code needs to be defined. It would be possible to just add a new command that as an example prints the name of the scope of a variable in debug-frontend-contribution:

        registry.registerCommand(DebugCommands.PRINT_SCOPE, {
            execute: () => {
                if (this.selectedVariable) {
                    let v: ExpressionContainer = this.selectedVariable;
                    while (v instanceof DebugVariable) {
                        v = v.parent;
                    }
                    if (v instanceof DebugScope) {
                        console.log(v.name);
                    }
                }
            },
            isEnabled: () => true,
            isVisible: () => true,
        });

with the necessary code on top of it. If a local variable is selected and the command PRINT_SCOPE is executed Local will be printed.

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[colin-grant-work]

This looks good to me. Since these are effectively tree items, it makes sense that they should satisfy more of the TreeItem interface, including a public parent field.