Test: Dynamic 'skipFiles' support and UI

[roblourens]

Test for #14728
Complexity: 4

Should probably cover both path types:

• Windows @ramya-rao-a
• MacOS/Linux @jrieken

We previously supported having the skipFiles attribute in the launch config. Now, you can also right click on a stack frame to skip or un-skip it.

Using node2, check these things:

• Skipped frames, whether by launch config or context menu, are grayed out in the callstack
• If you right click to skip/unskip a file, it is actually skipped/unskipped
• If a file is skipped by the launch config, it can be unskipped by right clicking

If you aren't sure what code to test, I usually write something like this:

a.ts:

import * as b from './b';

function f() {
  console.log('f');
}

b.callback(f);

b.ts

export function callback(cb) {
  cb();
}

Then you can easily verify that when b.ts is skipped, you can do a step-in to step directly from b.callback(f) to f.