Describe the feature:

In the inline documentation component we search both in titles and descriptions https://github.com/elastic/kibana/blob/main/packages/kbn-language-documentation-popover/src/components/documentation_content.tsx#L73

In the description we convert the JSX to a string first. Instead of doing this in every key stroke, we could store the documentation as string only for the search purposes, ideally in the CI job that creates the documentation.

So we can introduce a new property descriptionAsString that is being used only for search and we keep the Markdowns for the rendering.

Note: Also let's make everything lowercase in order to avoid lowercasing in the loop.