Bugfix: Loading state in DataViews when paginating

[chriszarate]

Currently when navigating through pages of results in DataViews, the user never sees a loading state. This is because the previous results continue to be passed to the component, which overrides the loading prop. This leads to some confusing "did it work?" UX:

before.mov

Instead we can withhold the results when the request is loading:

after.mov

Also noticing some alignment issues for the pagination links, not sure if that's because of our overlay or not. cc: @brookewp

[github-actions]

Test this PR in WordPress Playground.

[brookewp]

So strange! I'd be curious to see what the DOM looks like in your 'before', since the footer is fixed and shouldn't be moving 😕

Although I can't replicate this in trunk, this is a good safety measure to have, so thanks for adding it!