We don't consistently document how our SQL functions handle null values and other edge cases (such as negative integers in string function args). We should update the docs for each function so users know what to expect.

Due to the number of functions, we'll likely need to break this up over several PRs. We should prioritize string functions so we can document the changes in #68379

• Aggregate functions [DOCS] SQL: Document null handling for functions #74444
• Grouping functions [DOCS] SQL: Document null handling for functions #74444
• Date/Time and Interval Functions [DOCS] SQL: Document null handling for functions #74444
• Full-Text Search Functions (already done)
• Mathematical Functions [DOCS] SQL: Document null handling for functions #74444
• String Functions [DOCS] SQL: Document null handing for string functions #74201, [DOCS] SQL: Move string fn null/edge handling to arg descriptions #74255
• Type Conversion Functions [DOCS] SQL: Document null handling for functions #74444
• Geo Functions [DOCS] SQL: Document null handling for functions #74444
• Conditional Functions And Expressions (already done)
• System Functions (already done)

CC @astefan