The crash was due to some old logic that was looking for near matches.
Now we only return exact matches, and let the interpolation deal with
near matches.
Add test to make sure it doesn't crash at any value passed in.
Test: atest FrameworksCoreTests:android.content.res.FontScaleConverterTest
Bug: b/260984829
Change-Id: Ic90d1c5b48862e4f78b90be5926c9ce6d468acf9