fix(meta): disallow replacing tables with different engines

[zhyass]

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Summary

1. Reject CREATE OR REPLACE when an existing table uses a different engine.
2. Apply the check to regular tables, streams, atomic CTAS, and temporary tables.
3. Compare engine names case-insensitively.
4. Preserve the existing table, stream state, metadata, and data when replacement is rejected.
5. Add meta API and SQL regression tests for cross-engine replacement and same-engine replacement.

• fixes: bug(meta): Disallow creating or replacing same-named tables with different engines #20227

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test - Explain why

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):

AI assistance

• AI usage: An AI coding agent assisted with code analysis, implementation, and test drafting; I reviewed and verified the complete diff.
• Responsible human: @zhyass
• The responsible human has read every line of this diff and can explain each change

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This change is 

[drmingdrmer]

@drmingdrmer reviewed 2 files and all commit messages, and made 1 comment.
Reviewable status: 2 of 7 files reviewed, 1 unresolved discussion (waiting on dantengsky, SkyFan2002, TCeason, and zhyass).

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src/meta/api/src/api_impl/table_api.rs line 379 at r1 (raw file):

                                if !existing_meta
                                    .engine
                                    .eq_ignore_ascii_case(&req.table_meta.engine)

why is this check done only when as_dropped is set? the codes does not tell the reason behind it.

Code quote:

                            if req.as_dropped {
                                // CTAS does not call construct_drop_table_txn_operations(),
                                // so validate its existing table here.
                                let existing_meta =
                                    self.get_pb(&TableId::new(*id.data)).await?.ok_or_else(|| {
                                        KVAppError::AppError(AppError::UnknownTableId(
                                            UnknownTableId::new(
                                                *id.data,
                                                "create or replace failed to find existing table meta",
                                            ),
                                        ))
                                    })?;
                                if !existing_meta
                                    .engine
                                    .eq_ignore_ascii_case(&req.table_meta.engine)