[changelog] Let bootstrapping changelog consumer consumes after-image

[sixpluszero]

[changelog] Let bootstrapping changelog consumer consumes after-image

Make bootstrapping consumer also consume after-image data from version topic, instead of before-after image data from cc topic. Fixed a few small bugs during the journey, and clean up the integration tests.
Bugs:

1. seekToChekpoint needs to be blocked by get(), otherwise consumer will jump to non-deterministic offsets and yield wrong results.
2. when persisting after-image values to local storage, we should extra bytes from ByteBuffer, instead of converting to array directly.

How was this PR tested?

Added new integration tests and clean up old ones. Now we have 1 integration tests that cover ingestion bootstrapping consumer with/without bootstrap and 1/3 parallel consumers, which replace a few integration tests that serve the same purpose but with a lot of duplication in code.
For the existing TestChangelogConsumer#testAAwithStoreView(), I fixed the flakiness in the test, but the test is still too big and messy, consider refactoring it in the future.

Does this PR introduce any user-facing changes?

Bootstrapping changelog consumer will only consume after-image change events now.

• No. You can skip the rest of this section.
• Yes. Make sure to explain your proposed changes and call out the behavior change.

[gaojieliu]

Is this change still necessary as we are planning to deprecate after-image support?
cc @ZacAttack

[sixpluszero]

Is this change still necessary as we are planning to deprecate after-image support? cc @ZacAttack

This is the intended direction to switch from before/after to after-only image for bootstrapping changelog consumer.

[ZacAttack]

This overall looks good, just some nits

[ZacAttack]

Looks good!