Create inset adjusted alternative to `topActivityLetterboxHeight`

`topActivityLetterboxHeight` does not exclude insets and thus
inaccurately represents the apps true height. For non resizable
applications we must calculate their aspect ratio in order to respect
in throughout desktop windowing. `topActivityLetterboxHeight` when used
leads the wrong aspect ratio and causes the application to no fit the
window leading to black bars being shown.

Instead introduce `topActivityLetterboxAppHeight` and
`topActivityLetterboxAppWidth` (for consistency) which reflect the
configuration appBouunds as apposed to the bounds.

Flag: NONE(bug fix)
Test: presubmit
Fixes: 354918868
Change-Id: I18703d287fd77a640a30d45d9f927f41b3c91b43