feat(duckdb): Add transpilation support for INSERT function

[fivetran-amrutabhimsenayachit]

SQLGlot transpiles Snowflake INSERT to STUFF (T-SQL), which does not exist in DuckDB. All cases fail with: Catalog Error: Scalar Function with name stuff does not exist

python3 -c "import sqlglot; print(sqlglot.transpile(\"SELECT INSERT('Hello World', 7, 5, 'SQLGlot') AS typical_replace, INSERT('Hello', 6, 0, '!') AS append_end, INSERT('Hello', 3, 0, 'XY') AS pure_insert, INSERT('Hello', 2, 3, '') AS delete_chars, INSERT('Hello', 0, 0, 'X') AS pos_zero, INSERT('Hello', 10, 0, 'X') AS pos_beyond\", read='snowflake', write='duckdb')[0])"         
-->
SELECT SUBSTRING('Hello World', 1, 7 - 1) || 'SQLGlot' || SUBSTRING('Hello World', 7 + 5) AS typical_replace, SUBSTRING('Hello', 1, 6 - 1) || '!' || SUBSTRING('Hello', 6 + 0) AS append_end, SUBSTRING('Hello', 1, 3 - 1) || 'XY' || SUBSTRING('Hello', 3 + 0) AS pure_insert, SUBSTRING('Hello', 1, 2 - 1) || '' || SUBSTRING('Hello', 2 + 3) AS delete_chars, SUBSTRING('Hello', 1, 0 - 1) || 'X' || SUBSTRING('Hello', 0 + 0) AS pos_zero, SUBSTRING('Hello', 1, 10 - 1) || 'X' || SUBSTRING('Hello', 10 + 0) AS pos_beyond

│ typical_replace │ append_end │ pure_insert │ delete_chars │ pos_zero │ pos_beyond │
│     varchar     │  varchar   │   varchar   │   varchar    │ varchar  │  varchar   │
├─────────────────┼────────────┼─────────────┼──────────────┼──────────┼────────────┤
│ Hello SQLGlot   │ Hello!     │ HeXYllo     │ Ho           │ XHello   │ HelloX     │
└─────────────────┴────────────┴─────────────┴──────────────┴──────────┴────────────┘