Instance - Source filter/facet

Purpose:
This UI implementation of the Source filter covered by MSEARCH-4

User story statement(s):
As a librarian searching inventory
I want to be able to narrow my search by source
so that I can quickly find records that have underlying SRS records or are native to FOLIO

Scenarios:

1. Scenario:
   • Given Inventory-es app
   • When the landing page opens on the Instance tab
   • Then the Source filter displayed in the left pane and it is collapsed
     
2. Scenario:
   • Given the Source filter is collapsed
   • When the user clicks on the filter
   • Then the filter expands and displays two checkboxes: FOLIO and MARC
   • 
3. Scenario:
   • Given the Source filter/facet
   • When the user selects a checkbox
   • Then search results are populated with the instances matching selected source
4. Scenario:
   • Given the user searched using keywords textbox
   • When the results are populated
   • Then the Source filter/faucet is expanded and shows record count for each source

Out of scope: Entering same search in search box and selecting filter