Support thousand separator for floating point numbers

[Mytherin]

Implements #11657

Example usage:

select printf('%,.2f', 123456789.456);
┌────────────────────────────────┐
│ printf('%,.2f', 123456789.456) │
│            varchar             │
├────────────────────────────────┤
│ 123,456,789.46                 │
└────────────────────────────────┘