Since {rBeae36be372a6b16ee3e76eff0485a47da4f3c230} the distinction
between float and byte colors is more explicit in the ui. So far, geometry
nodes couldn't really deal with byte colors in general. This patch fixes that.
There is still only one color socket, which contains float colors. Conversion
to and from byte colors is done when read from or writing to attributes.

* Support writing to byte color attributes in Store Named Attribute node.
* Support converting to/from byte color in attribute conversion operator.
* Support propagating byte color attributes.
* Add all the implicit conversions from byte colors to the other types.
* Display byte colors as integers in spreadsheet.

Differential Revision: https://developer.blender.org/D14705