Show metrics in a (more) human-readable format

Ideally we could find a way to make the Flink metrics protos available to the Python client without `toString`, since `toString` should generally should be human-readable. The problem is that without a job server, there's nowhere to access job information like metrics outside of what Flink provides natively.
 
This issue was introduced here: [https://github.com/apache/beam/pull/11369/files#diff-7fd541906a9e771c3312b75947e969daL176](https://github.com/apache/beam/pull/11369/files#diff-7fd541906a9e771c3312b75947e969daL176)

Imported from Jira [BEAM-10719](https://issues.apache.org/jira/browse/BEAM-10719). Original Jira may contain additional context.
Reported by: ibzib.

Start with the code introduced by the linked Apache Beam pull request, focusing on the Python client’s handling of Flink metrics protos and its use of toString. Investigate how job information is exposed without a job server; done means metrics are available to the Python client in a human-readable format without relying on toString.

Written by the indexing model from the issue text.