[Figma] Lead space search

Updates to the component in v2:

[x] Variant with an image background has been deprecated in v2
[x] Removed title and subheading discrepancy. Now there is only one heading for the component.
[x] New highlight span can be added to the heading (no where else). Highlight can apply to a word or words anywhere in the heading.
[x] New Dotcom color token to handle highlight across lead space components: $heading-highlight.
[x] Updated spacing values to bring in line with content block/section. Margin at top and bottom.
[x] No more 90% container width for text. Text width is now more in-line with content block (instead of 90% of container)
[x] Use Carbon core's search set to the large sizing.
[x] Search is now flush with the columns (no overhang)

carbon-design-system / carbon-for-ibm-dotcom-design-kit