Remove virtual function in RowReader

[critical27]

What type of PR is this?

• bug
• feature
• enhancement

What problem(s) does this PR solve?

Issue(s) number:

Description:

Since we don't support data of 1.x long ago, we don't need the virtual interface of RowReader anymore. So I removed RowReader and RowReaderV1.

RowReaderWrapper now only contains a pointer of RowReaderV2. No more virtual function called.

After this PR, the virtual interface of SchemaProviderIf could be removed as well, I'll handle it later

How do you solve it?

Special notes for your reviewer, ex. impact of this fix, design document, etc:

@HarrisChu, this PR may or may not improve the performance, could pay some attention to it later.

Checklist:

Tests:

• Unit test(positive and negative cases)
• Function test
• Performance test
• N/A

Affects:

• Documentation affected (Please add the label if documentation needs to be modified.)
• Incompatibility (If it breaks the compatibility, please describe it and add the label.）
• If it's needed to cherry-pick (If cherry-pick to some branches is required, please label the destination version(s).)
• Performance impacted: Consumes more CPU/Memory

Release notes:

Please confirm whether to be reflected in release notes and how to describe:

ex. Fixed the bug .....

[cangfengzhs]

Since you modified it, why is it still called RowReaderV2? V2 can be deleted

[critical27]

Since you modified it, why is it still called RowReaderV2? V2 can be deleted

For now, just keep the old naming, there is also a RowWriterV2...
All code use RowReaderWrapper, we could remove it and rename RowReaderV2 to RowReader together if necessary.

[pengweisong]

Good job

[dutor]

LGTM.