Add SDK_MINOR_INT

Introduce Build.VERSION.SDK_MINOR_INT. This functions like SDK_INT, but
represents the minor version of the Android API level; SDK_INT
corresponds to the major version.

Yearly dessert releases will increment SDK_INT and set SDK_MINOR_INT to
zero. In-between desserts there may be additional, minor, releases where
SDK_INT is kept the same and SDK_MINOR_INT is incremented.

A minor release may include new APIs and resources, but must not
introduce any back compat changes. Specifically, this means that minor
releases are optional and guaranteed to not require developers to
rebuild their apps.

Bug: 350458259
Test: m
Flag: android.sdk.major_minor_versioning_scheme
Change-Id: I10d39f33ecfbd463753585224d674ceaefe83b22