format: expose functions/procedures in catalog metadata

[lidavidm]

What feature or improvement would you like to see?

Add a GetObjectsFunctions and related functions to show user-defined and system functions, aggregate functions, table-valued functions, and stored procedures.

Prior Art

• JDBC: getSystemFunctions
• JDBC: getFunctions
• JDBC: getFunctionColumns
• JDBC: getProcedures
• JDBC: getProcedureColumns
• ODBC: SQLProcedures
• ODBC: SQLProcedureColumns()
• BigQuery: Feature Request: Comprehensive Metadata Discovery for Data Development Tools adbc-drivers/bigquery#118
• Databricks: Feature Request: Enhanced Metadata Discovery for Databricks ADBC Driver adbc-drivers/databricks#236
• PostgreSQL: Feature Request: [postgresql] Comprehensive Metadata Discovery for Data Development Tools #3971
• Snowflake: Feature Request: Comprehensive Metadata Discovery for Data Development Tools adbc-drivers/snowflake#77
• Trino: [Go] Feature Request: Comprehensive Metadata Discovery for Data Development Tools adbc-drivers/trino#60

Design Issues

• Do we expose system functions, etc. in the same function?
• Do we expose procedures in the same function?
• How do we expose signatures?
• How do we expose overloads?
• How do we provide Arrow-equivalent signatures?
• How do we handle database-specific properties?

Proposal

TBD