Add support for float type in FRRO

This can be used to overlay a resource in the form
<item name="testFloatDimen" format="float" type="dimen">0.015</item>.

Test: atest FabricatedOverlaysTest
Bug: 369672322
Flag: android.content.res.dimension_frro
Change-Id: I3e7f4c811801be46d42e2b08a8924a3fa878d3c4