feat: generated and identity columns for mssql, sqlite, drizzle, typeorm, bun and gorm readers

- mssql: write computed columns (AS (expr) PERSISTED) and identity; read computed definition and identity
- sqlite: write GENERATED ALWAYS AS (expr) STORED; read generated columns via table_xinfo and parse the expression
- drizzle: generatedAlwaysAs / generated(Always|ByDefault)AsIdentity, read and write
- typeorm: asExpression/generatedType and identity decorators, read and write; decorator scan is now quote-aware
- bun, gorm readers: read generated and identity markers
- readmes updated

pkg/writers/drizzle/README.md

@@ -113,6 +113,7 @@ export const postsRelations = relations(posts, ({ one }) => ({
 
 ## Notes
 
+- Generated columns: `.generatedAlwaysAs(sql`expr`)`; identity columns: `.generatedAlwaysAsIdentity()` / `.generatedByDefaultAsIdentity()`
 - Table names and column names are preserved as-is
 - Relationships are generated as separate relation definitions
 - Constraint actions (CASCADE, etc.) are included in references