Add support for inferring Beam Schemas from Python protobuf types

Just as we can infer a Beam Schema from a NamedTuple type ([code](https://github.com/apache/beam/blob/master/sdks/python/apache_beam/typehints/schemas.py)), we should have support for inferring a schema from a [protobuf-generated Python type](https://developers.google.com/protocol-buffers/docs/pythontutorial).

This should integrate well with the rest of the schema infrastructure. For example it should be possible to use schema-aware transforms like [SqlTransform](https://beam.apache.org/releases/pydoc/2.32.0/apache_beam.transforms.sql.html#apache_beam.transforms.sql.SqlTransform), [Select](https://beam.apache.org/releases/pydoc/2.32.0/apache_beam.transforms.core.html#apache_beam.transforms.core.Select), or [beam.dataframe.convert.to_dataframe](https://beam.apache.org/releases/pydoc/2.32.0/apache_beam.dataframe.convert.html#apache_beam.dataframe.convert.to_dataframe) on a PCollection that is annotated with a protobuf type. For example (using the addressbook_pb2 example from the [tutorial](https://developers.google.com/protocol-buffers/docs/pythontutorial#reading-a-message)):

```

import adressbook_pb2

import apache_beam as beam
from apache_beam.dataframe.convert import to_dataframe

pc
= (input_pc | beam.Map(create_person).with_output_type(addressbook_pb2.Person))

df = to_dataframe(pc)
# deferred dataframe with fields id, name, email, ...

# OR

pc | beam.transforms.SqlTransform("SELECT
name WHERE email = 'foo@bar.com' FROM PCOLLECTION")

```

Imported from Jira [BEAM-12955](https://issues.apache.org/jira/browse/BEAM-12955). Original Jira may contain additional context.
Reported by: bhulette.