fix: correct namespaceId jdbcType bindings(#6718)

[juicewcode]

Fixes #6718

Summary

• Changed the namespaceId JDBC type in the meta_data insert statement from TINYINT to VARCHAR
• Changed the namespaceId JDBC type in the namespace_plugin_rel query condition from TINYINT to VARCHAR
• Added mapper tests for string namespace IDs

Test

• Tested inserting and reading back a non-numeric string namespace ID in meta_data
• Tested filtering namespace_plugin_rel records by a string namespace ID

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• You submit test cases (unit or integration tests) that back your changes.
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