Add language facet - add state and data

What does this MR do and why?

Vuex state and data fetch for the language filter components.

set of MRs	status
Add language facet - feature flag	in review
Add language facet - add state and data	👈 this MR
Add language facet - add components	in review

Screenshots or screen recordings

How to set up and validate locally

1. Enable the language aggregation

   echo 'Feature.enable(:search_blobs_language_aggregation)' | rails c

2. Visit the search page http://gdk:3000/search
3. Scope blob will have a language filter in a followup MR.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #342651 (closed)