feat: Support USE CATALOG syntax and current_catalog() function

[flashmouse]

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Summary

• fixes: Feature: Support USE CATALOG syntax and current_catalog() function #16848

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):

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This change is 

[flashmouse]

I observe that use_database statement is prior to use_catalog unless I quote #ident(catalog)

use catalog abc  // parse to UseDatabase{"catalog "} which is unexpected
use catalog `abc` //  parse to UseCatalog{"abc"} correctly

[flashmouse]

@b41sh please help me check if it is suitable now

[b41sh]

Hi @flashmouse Seems almost OK for me. Better to add some test cases in tests/suites/3_stateful_iceberg/00_rest/00_0000_create_and_show.sh and tests/suites/3_stateful_iceberg/00_rest/00_0000_create_and_show.result

[flashmouse]

Hi @flashmouse Is this PR ready to review? Seems almost OK for me. Better to add some test cases in tests/suites/3_stateful_iceberg/00_rest/00_0000_create_and_show.sh and tests/suites/3_stateful_iceberg/00_rest/00_0000_create_and_show.result

I would mark this as ready to review after add test as you advice.