Update vhal_const_generate to emit all known values

Instead of hard coding the enum collections of interest, the generator
now iterates over all known enums in the VHAL API and emits python
symbols for all of them.
This change also includes updates to the symbol names to standardize
them to facilitate machine generation.
Test:  Run vhal_emulator_test.py (fails on one value, it does that
before my change)

Change-Id: Iaa6bc492159180cc5ad597ec5cc666fdb25b290e
7 files changed