Fix behavior change due to incorrect initial floating setting

[mehmetf]

Description

customer:money observed a regression in InputDecoration due to 6852605. Looking through code, I realized that the isInitiallyFloating parameter is not correctly obeying the newly introduced FloatingLabelBehavior.

Related Issues

None.

Tests

I added the following tests:

I am not entirely sure what the initiallyFloatingLabel does but I noticed that there is a dy difference when it is set to true vs false. I am checking that the correct value is now set when FloatingLabelBehavior is set to never.

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Breaking Change

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[justinmc]

LGTM 👍 Thanks for catching and fixing this. The failures seemed like unrelated infrastructure things.