Include headers/footers in EmptySource count so they show up when ItemsSource is null

[hartez]

Description of Change

The EmptySource on Android is aware of the header and footer, but doesn't include them in the Count. Which means that the adapters don't know to display them when the ItemSource is null.

This change adjusts the reported Count from EmptySource to account for the presence of the header and footer.

This is an alternate (and more correct) solution to #15688.

Issues Fixed

Fixes #8934

[PureWeen]

Can we add some additional tests that would cover the case(s) found by the legacy gallery?

[mattleibow]

/rebase

[mattleibow]

I see the less correct #15688 is merged... yuet no conflicts even since it touches the same files...

[mattleibow]

I see it was reverted actually: #15886

This is the issue that Shane was referring to: https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=7979402&view=ms.vss-test-web.build-test-results-tab

[hartez]

Can we add some additional tests that would cover the case(s) found by the legacy gallery?

Aren't they covered by the legacy gallery tests?

[PureWeen]

Can we add some additional tests that would cover the case(s) found by the legacy gallery?

Aren't they covered by the legacy gallery tests?

We only run these tests on the main/feature branches. Ideally, we'll grow enough coverage inside our new appium tests/device tests (which run on every PR) that we can eventually just obsolete our legacy gallery tests once we feel that we've pretty much reached coverage parity.