pkg/executor: report MV refresh and purge statement results

[windtalker]

What problem does this PR solve?

Issue Number: N/A

Problem Summary:
Reopen the previously merged statement-result change on top of the current mv_test branch.
This keeps the same behavior change for MV refresh / purge statement results after the base branch history moved.

What changed and how does it work?

• report statement affected rows and last message for fast refresh and complete delta apply from internal executors
• propagate statement results back to the outer session for all refresh modes and purge materialized view log
• keep the no-op fast as of timestamp result behavior
• carry over the targeted regression tests from the previous branch

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

Manual test steps:

• recreated the PR branch from current mv_test by cherry-picking the original three commits
• verified the diff against xufei/mv_test matches the expected statement-result changes
• previous equivalent branch was reviewed in pkg/executor: report MV refresh and purge statement results #49

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

None