Add 32BIT and 16BIT nanopb library.

Add 32BIT and 16BIT compile time flag for nanopb library to support
16BIT or 32BIT size, default is 8BIT. User need to use the corresponding
library when define the PB_FIELD_* flag during compilation.

Change-Id: I0d25bcdf62d6b47733e1ad4bddbd4dfce2192b5d
Test: None
Bug: 122292884