feat(GlIcon): update validator for deprecated icons sizes

What does this MR do?

Contributes to #1232 (closed)

This MR updates a validator for GlIcon size and will log a warning when an icon size that is outside the allowed sizes list is used. At the same time, it allows to suppress the warning by providing useDeprecatedSizes property to GlIcon. Code that generates icon size CSS classes still uses deprecated list as 18 && 10 size values are used in GitLab codebase.

This is a temporary change until we update all instances of GlIcon in GitLab codebase to use only allowed icon sizes.

GitLab integration MR - gitlab!55638 (merged)

Does this MR meet the acceptance criteria?

Conformity

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• Added the ~"component:*" label(s) if applicable.

Security

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Accessibility

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• All actions and functionality can be done with a keyboard.
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