[Android][0] and [Desktop][1] have already removed this field. This
follows suit.
The highlights:
- `SignalService.proto` removes some fields by making them `reserved`
- `ProtoWrappers.py` updates our code generation to support addresses
that only have a UUID (previously, you needed both a UUID and E164
field)
- Most everything else is removing E164s
[0]: 9c266e7995
[1]: 2b0d3cab40
We can only *really* trust this once the certificate validates, and
even then the certificate could be out of date. So now the mapping is
only treated as high-trust when the inner messages decrypts
successfully too.
