Fix #25199: Add database-level tag inheritance support

[10elements]

Describe your changes:

Fixes #25199

Implements tag inheritance from database -> schema -> table for Snowflake connector. Previously only schema -> table inheritance was supported.

Changes:

• Add SNOWFLAKE_FETCH_DATABASE_TAGS query to fetch database-level tags
• Add database_tags_map storage and set_database_tags_map() method
• Add yield_database_tag() to expose database tags to topology
• Update get_schema_tag_labels() to inherit database tags
• Update get_tag_labels() to inherit both schema and database tags
• Implement tag value precedence: lower-level values override inherited values (e.g., if both database and table have ENV tag, table's value wins)
• Add unit tests for database tag inheritance and tag value precedence

Type of change:

• Bug fix
• Improvement
• New feature
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation

Checklist:

• I have read the CONTRIBUTING document.
• My PR title is Fixes <issue-number>: <short explanation>
• I have commented on my code, particularly in hard-to-understand areas.
• For JSON Schema changes: I updated the migration scripts or explained why it is not needed.

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Summary by Gitar

• Database tag support:
  • New SNOWFLAKE_FETCH_DATABASE_TAGS query and set_database_tags_map() method fetch and store database-level tags
• Three-level inheritance:
  • Implements database → schema → table tag propagation with precedence rules (lower-level values override inherited ones)
• Test coverage:
  • Added test_database_tag_inheritance() and test_tag_value_precedence() covering inheritance chains and conflict resolution

_{This will update automatically on new commits.}

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