Addresses #14127.

This implements an exclude list to the smoke test definition that should help to exclude a test from a specific runner or all runners.

Example:

 export default {
   id: 'foo',
   expectations,
   config,
+  exclude: ['devtools', 'cli'],
 };

A test can be excluded from all runners by specifying exclude: ['*'].

In order to temporarily ignore an exclusion for debugging, Smoke CLI now features a boolean flag --ignore-exclusions.

@connorjclark I chose to retain the list as a fixed structure instead of exclude being a boolean.