Support navigation and globals in the static caching invalidation

[jasonvarga]

Duncan's PR #2639 was wiping out all the URLs when you edit a nav or global. Rather, you can define the URLs like you can with collections and taxonomies.

'invalidation' => [

    'rules' => [
        'globals' => [
            'settings' => [
                'urls' => [
                    '/*'
                ]
            ]
        ],
        'navigation' => [
            'links' => [
                'urls' => [
                    '/*'
                ]
            ]
        ]
    ],

],

In there, you're free to just tell it to wipe them all, if that's what you want.

Also clean up tests by using regular mocks, not spies, and do a little tidying.

Closes #2639
Closes #2393