Allow Commit.RawBlame to take a Range parameter
Git supports a wide array of range options for this option, but for now we restrict the formats we support to the very simplest, which is of the form "1,100".
We can use this to implement limits on how many lines of the blame we retrieve GitLab-side, which should help to reduce the resource usage of this particular RPC.
Related to gitlab#225174 (closed)
Changelog: added