VERSION_CODES_FULL docs: use Android versions

Change the VERSION_CODES_FULL Javadoc to refer to Android versions (e.g.
"Android 4.1" for Jellybean) instead of the FULL_SDK_INT values (e.g.
"16.0" for Jellybean).

The versions have been taken from https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels.

Bug: 442220715
Bug: 442320779
Test: lunch sdk-next-eng && m docs dist
Flag: EXEMPT improved docs on existing APIs
Change-Id: I2922903d77f43df3c2050ff533c2173ac545028d