The output of this task is to refactor sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/pubsub/PubsubSchemaIOProvider.java to extend TypedSchemaTransformProvider.

This task will be separated into four PRs to focus on Read and Write SchemaTransforms and their respective Configurations. See BigQuerySchemaTransformReadProvider and BigQuerySchemaTransformWriteConfiguration as an example design pattern.

Imported from Jira BEAM-14036. Original Jira may contain additional context.
Reported by: laraschmidt.
Subtask of issue #21406