Extract VHeader as a wrapper for header and banners

[obulat]

Fixes

Fixes #4764 by @obulat

Description

This PR extracts VHeader component (wrapper over the VBanners and VHeader<Internal|Desktop|Modal>). This allows us to only have the height computation, saved in a CSS variable, necessary to correctly set the modal height and offset in search layout both when the banners are visible and when they are not.

Testing Instructions

The CI should pass and the header should work correctly on all layouts (content pages, home page, search pages).

Checklist

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[zackkrida]

Suggested change

	const comp = computed(() => {
	const comp = computed(() => {

Nit: comp is kinda overloaded with "computed" and "component": How about "headerComponent" instead?

[zackkrida]

Working great, lgtm. I left one suggestion.