[FLINK-32418][formats-protobuf] Fix ClassNotFoundException when using protobuf in SQL-Client

[m-kay]

Purpose of the change

This pull request changes protobuf format to always use the classloader which is passed on creation for the DynamicTableFactory.Context instead of using the thread local classloader as proposed in FLINK-32418. This is needed to load generated protobuf classes when using the protobuf format in SQL-Client.

Change log

• The classloader passed in DynamicTableFactory.Context is stored in a PbFormatContextwhich is then passed further down the components
• PbFormatUtils.getDescriptor has an additional parameter where the classloader from the PbFormatContaxt has to be passed to resolve generated Protobuf classes correctly.

Verifying this change

This change is already covered by existing tests, such as SimpleProtoToRowTest.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: yes
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no

[flinkbot]

CI report:

• a653468 Azure: FAILURE

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[libenchao]

@m-kay Thanks for your contribution, and sorry for the delay, the PR looks good generally, I'm just wondering if it's possible to have a test case which shows the problem and passes after this fix?