Add pretty printing to more sql constructs

This is a followup on https://github.com/apache/datafusion-sqlparser-rs/pull/1847

Here are some constructs that are currently not handled by the pretty printer (they are displayed on a single line). I'm opening this to serve as a tracking issue to track implementation of these.

* [x] Format `INSERT INTO` with both `VALUES` and `SELECT` forms
* [x] Support `UPDATE` and `DELETE` with proper clause indentation
* [x] indent `CREATE TABLE` column definitions and constraints
* [x] Format `CREATE VIEW` and nested `SELECT` cleanly
* [ ] Handle `CREATE FUNCTION`/`PROCEDURE` blocks with inner SQL formatting
* [ ] format `json_table` and `xmltable`
* [ ] Format `BEGIN`, `COMMIT`, `ROLLBACK` blocks clearly
* [ ] Support control flow structures (`IF`, `WHILE`, `LOOP`) with block indentation
* [ ] support multiline strings (the indentation should not be reflected inside the string)
* [ ] Handle `MERGE` statements with `WHEN MATCHED` and `WHEN NOT MATCHED` branches
* [ ] format `CREATE INDEX` with minimal structure
* [ ] Handle `EXPLAIN`, `EXPLAIN ANALYZE`, and `DESCRIBE` statements

cc @alamb

Das Issue nennt keine Dateien, Tests oder Einstiegspunkte. Überprüfe die nicht abgehakten Checklistenpunkte und kläre ihren Umfang sowie die erwartete Formatierung, bevor du beginnst; erledigt bedeutet, dass die ausgewählten SQL-Konstrukte mittels Pretty-Printing mit der erforderlichen Einrückung und Zeichenkettenbehandlung formatiert werden.

Vom Indexierungsmodell aus dem Issue-Text verfasst.