Added some DragValue widgets in the color_picker widget as input fields
for managing the RGBA values.
In case the provided values result in a not valid premultiplied alpha
RGBA color, a button will appear next to the input fields, to be used to
multiply the values with the alpha channel.

Closes <https://github.com/emilk/egui/issues/2716>.
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Co-authored-by: IVANMK-7 <68190772+IVANMK-7@users.noreply.github.com>
Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
Co-authored-by: Brian Janssen <tosti007@users.noreply.github.com>
* split out ecolor crate
* split up ecolor crate in lots of modules
* add changelog notes
* add readme to ecolor
* put clippy::manual_range_contains on cranky allow list
* fix hex color issues
* doc fixes
* more hex_color fixes
* Document features
* Rename hex_color module to avoid warning
* Sort the feature names
* fix link in CHANGELOG.md
* better wording
Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>