insights: [spike] investigate methods for lines of code calculations

Created by: leonore

having an insight for lines of code per language across multiple repos is a common customer request.

there's ways of doing this with compute (content:output(.*\n -> $lang) count:all) and it works across small repos but there's some problems with it:

• monorepo performance is bad (doesn't work)
• performance across multiple repos is bad

this issue is about investigating whether this would be feasible to do over the filesystem (hitting gitserver) instead of search