fix(iceberg): Table desc should allow nested db_name

[Xuanwo]

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Summary

Table desc should allow nested db_name

Tests

• [x] Unit Test
• [ ] Logic Test
• [ ] Benchmark Test
• [ ] No Test - Explain why

Type of change

• [x] 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):

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This change is 

[BohuTANG]

Add some logic tests for the iceberg table?

[Xuanwo]

Add some logic tests for the iceberg table?

Tests will be added as a whole. There are the following PRs to address other issues.