[HUDI-7176] Add file group reader test framework

[linliu-code]

Our goal is to add a framework for unit tests at the level of file group reading. That is,
we don't need to involve any engine specific logic during the read, such that we could

1. Simplify the test process by providing unified and simple APIs,
2. Impose more granular read process for testing, and
3. Improve the test performance since no engine specific logic are involved.

We will add the framework step by step.

Change Logs

Steps:

1. Add a builder class to construct file group reader.

Impact

1. Simplify the process to construct file group reader level tests;
2. Improve the test performance by removing engine specific logic.

Risk level (write none, low medium or high below)

None.

Contributor's checklist

• Read through contributor's guide
• Change Logs and Impact were stated clearly
• Adequate tests were added if applicable
• CI passed

[linliu-code]

@yihua , @codope , @danny0405

[hudi-bot]

CI report:

• 9450ab6 UNKNOWN
• 15f28aa Azure: SUCCESS

Bot commands

@hudi-bot supports the following commands:

• @hudi-bot run azure re-run the last Azure build

[linliu-code]

@yihua, I have addressed your comments. My overall plan is to land this PR, and use another PR to further simplify this framework and integrate more with other existing modules. How does it sound?

[yihua]

+1