Limit time frame when calling Gitaly for commit history

gitaly#5426 (moved) details a performance limitation with huge repos (46gb) where FindCommits calls are timing out. This is due to the size of the commit history and Git having to look through the entire tree. The discussion determined that the most practical way to solve this performance limitation is for the Rails client to call Gitaly by limiting the timeframe in which commits will be searched.

This issue is about changing Rails to call FindCommits with After to limit the amount of commits Git has to search through.

Proposal

Provide url parameters committed_before and committed_after to filter the commits by date range.