[@mantine/core] ColorInput: Add support for fullWidth prop

[saadpocalypse]

Problem

The ColorPicker component supports taking 100% width of its container using the fullWidth prop. However, when rendering ColorPicker within a ColorInput dropdown, there was no way to pass the fullWidth prop from ColorInput down to the picker. Additionally, because the popover dropdown has width: 'max-content' by default, passing a 100% width constraint directly to the child color picker caused the layout to collapse.

Solution

• Moved the fullWidth prop from ColorPickerProps to __ColorPickerProps so that it is properly inherited by ColorInputProps.
• Forwarded fullWidth from ColorInput to the internal <ColorPicker /> component.
• Passed width={fullWidth ? 'target' : undefined} to the <Popover /> wrapper inside ColorInput so that the dropdown matches the target input's width and prevents the picker layout from collapsing.

Tests

• Unit Tests: Added a test case in ColorInput.test.tsx to verify that passing fullWidth to ColorInput correctly applies the data-full-width attribute to the underlying picker wrapper inside the dropdown.
• Visual Stories: Added a FullWidth story in ColorInput.story.tsx with popoverProps={{ opened: true }} to demonstrate the color picker expanding to the full width of the input dropdown.

Resolves #9060