gqltest: add search integration tests

Created by: unknwon

Adds integrations tests for search, which covers:

• repository group
• global text search:
  • (error) with many results
  • (error count:>1000), expect many results
  • for something with more than 1000 results and use "count:1000"
  • for a regular expression without indexed search: (index:no ^func.*$), expect many results
  • fork:only, few results
  • fork:no, 0 results
• global filename search:
  • with 0 results
  • with many results
• global symbol search:
  • with 0 results
  • ("type:symbol ^newroute count:100") with a few results

Please review by commit.

Part of #10068 (closed)