Implement fallback line spacing for BoringLayout

The fallback line spacing is a feature of extending the line height
when the fallback font has taller glyph. This was implemented to
StaticLayout in Android P but not yet implemented in BoringLayout.

This CL enables this feature to the BoringLayout as well.

Not to break existing apps, change this behavior only if the
targetSdk version is T or later.

This is a 2nd attempt of Ia6d6f9f44e73ddaf5e8fe9a8aead7a53efbddd44
The root cause of SystemUI crash was wrong API usage. (start, end) was
passed instead of (start, count).

Bug: 210923482
Test: atest FallbackLineSpacingTest BoringLayoutFallbackLineSpacingTest
Test: atest CtsGraphicsTestCases
Test: atest CtsTextTestCases
Test: atest SystemUITests
Change-Id: I9137607b0120934f7ad2a12c0f0b8aaa52915831