This means the betterproto plugin no longer needs to depend durectly on
protobuf.

This requires a small runtime hack to monkey patch some google types to
get around the fact that the compiler uses proto2, but betterproto
expects proto3.

Also:
- regenerate google.protobuf package
- fix a regex bug in the logic for determining whether to use a google
  wrapper type.
- fix a bug causing comments to get mixed up when multiple proto files
  generate code into a single python module

- Remove plugin dependency on protobuf since it's no longer required.
- Update poethepoet to for better pyproject toml syntax support
- Add handy generate_lib poe task for maintaining generated libs

…r-cli-interface

# Conflicts:
#	tests/test_features.py

# Conflicts:
#	poetry.lock
#	pyproject.toml
#	src/betterproto/plugin/main.py
#	src/betterproto/plugin/models.py
#	src/betterproto/plugin/parser.py
#	tests/inputs/oneof/test_oneof.py
#	tests/util.py

# Conflicts:
#	README.md
#	pyproject.toml
#	src/betterproto/plugin/compiler.py
#	src/betterproto/plugin/main.py
#	src/betterproto/plugin/models.py
#	src/betterproto/plugin/parser.py
#	tests/generate.py
#	tests/test_features.py
#	tests/util.py