Respect diff.algorithm in gix blame

[cruessler]

Currently, the diff algorithm used for diffing while running blame is hard-coded to Histogram in blame::file() (or, more specifically, in blob_changes()). With this PR, diff_algorithm becomes an option to be provided to blame::file(). For gix blame, the value of diff.algorithm as returned by Repository::diff_algorithm() is used.

• feat!: add diff_algorithm to blame::file()
• Adapt to changes in gix-blame

[Byron]

That makes sense, thanks a lot!