Fix FloatingActionButtonLocation for additional test case

[Piinks]

Description

Adding on to this change: #60248
I realized while looking at #59272 and #59204 that I missed a case for the floating FloatingActionButtonLocations. The contentBottom of the Scaffold is affected by the BottomNavigationBar, and so needs to be taken into account for the float positions.

Related Issues

#59272
#59204
#60248

Tests

I added the following tests:

Added multiple configurations of BottomNavigationBar to the floating positional tests.
I also noticed upon revisiting that the positional arguments were a bit hard to follow, so I made them all named parameters in the related tests.

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Breaking Change

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[HansMuller]

LGTM. Excellent implementation to test coverage ratio!