[Discover] Use named color tokens for in-table highlights

[jughosta]

Originally suggested in #206454 (comment)

Let's create a dedicated issue for tracking this and working with the EUI team to get the tokens.

kibana/src/platform/packages/shared/kbn-data-grid-in-table-search/src/constants.ts

Lines 12 to 13 in 8ffb2ff

	export const HIGHLIGHT_COLOR = '#e5ffc0'; // TODO: Use a named color token
	export const ACTIVE_HIGHLIGHT_COLOR = '#ffc30e'; // TODO: Use a named color token

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)

[jughosta]

cc @l-suarez