cookie-consent dialog display flicker

[michaelwood]

Overrides in 360-ds are coming back to bite us, the .base-card class has been implemented on cookie-consent dialog but this sets a display property which is interfering with the toggling of the cookie-consent display, causing it to pop up and disappear on page load if an option (yes/no/no analytics) has already been made.

Two options for solving this, add another override #68 which works but is fragile, or fix it more sustainably and rewrite the dialog without using the existing modules from the design system, creating a completely new standalone component.

In general we are finding that the components/modules in the design system aren't generic enough to be re-usable. So this is an approach we may need to shift to.

[mariongalley]

Discussed with @robredpath - looks like the override bit is already more or less done, so although I don't like to kick problems down the road I'd suggest we use that rather than rewrite the dialog now. Would be good to keep documented somewhere that that still needs doing and include it in iterative improvements some time.