add option for input validation foreground color

[ParkourKarthik]

This closes #57536

@bpasero I've made changes only related to "find Input control".
Review and let me know if similar changes could be applied to all other input validations.

[bpasero]

@ParkourKarthik unless I am mistaken, these colors should not have any default set, otherwise we change the semantics, aren't we? Today I do not think we apply any particular foreground color by default and I think we should only do so if the theme defines this color explicitly.

Also, we need to support this color everywhere where the correlating background color is passed through, so please find all occurrences of where input background colors are used and pass them through.

[ParkourKarthik]

@bpasero I've set the default values to null. I believe that is meant to be done when no actual defaults are to be set.

Note: I've not added any Validation Foreground colors to the below as there should not be defaults for Foreground.
https://github.com/Microsoft/vscode/blob/8539f48172f1ba5acfe34bb5633eb684d59634ba/src/vs/base/browser/ui/inputbox/inputBox.ts#L72-L81

[bpasero]

@ParkourKarthik much better. There is one remaining usage of inputValidationInfoBackground in messageController that can also have a foreground color from the theme.

[bpasero]

Thanks 🍺