[BUG] In dark mode, auto-populated fields are tough to see

[AMoo-Miki]

Describe the bug

Input fields that are auto-populated by the browser, like a saved usernames, are too dark to see in the dark mode for both default and Next themes. That is because the "shades" are reversed in dark mode where $ouiColorLightestShade is in fact nearly black and $ouiColorDarkestShade is nearly while. The code below wrongly uses $ouiColorLightShade, which is a dark color, on a dark background.

oui/src/themes/oui-next/global_styling/mixins/_form.scss

Lines 265 to 277 in 0365b42

	&:-webkit-autofill {
	-webkit-text-fill-color: lightOrDarkTheme($ouiColorDarkestShade, $ouiColorLightShade);
	~ .ouiFormControlLayoutIcons {
	color: lightOrDarkTheme($ouiColorDarkestShade, $ouiColorLightShade);
	}
	/* OUI -> EUI Aliases */
	~ .euiFormControlLayoutIcons {
	color: lightOrDarkTheme($ouiColorDarkestShade, $ouiColorLightShade);
	}
	/* End of Aliases */
	}

$ouiColorDarkestShade or $ouiColorDarkShade are much more suitable for the dark themes input-fields.

Screenshots