[feat][txn] Add TxnID and TransactionCoordinatorClient support to TransactionV5

[TomaszGaweda]

Motivation

Many streaming engines need to operate on Transaction IDs to deal with exactly-once delivery guarantees.

Previously, in #26646 we've exposed TransactionCoordinatorClient to allow usage in such engines.

This PR does basically the same, but for V5 API, making it ready for streaming engines.

Modifications

Since v5 API does not depend on v4 API, I've copied TxnID and TransactionCoordinatorClient + Exceptions to v5. In PulsarClientV5 I'm returning this wrapped TransactionCoordinatorClient.
TransactionCoordinatorClientV5 just delegates tasks to v4 API, just like most other APIs.

Verifying this change

• Make sure that the change passes the CI checks.

Every test invoking transactions on V5 API will now test this change.

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

If the box was checked, please highlight the changes

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

[merlimat]

This was intentionally left out from the v5 API to avoid exposing internals.

I think it would be better to have a discussion on what it's needed instead of exposing the transaction client which is not meant to.

[TomaszGaweda]

@merlimat I am open to discussion, can share stream engine developer PoV :)

[merlimat]

@TomaszGaweda Definitely want to hear you PoV! Can you start a thread on the dev@pulsar.apache.org or a new GitHub discussion to explain what "help" do you need from the client API?