feat: enable lfs for git origin

[1-ashraful-islam]

• Allow the user to set enable_lfs = true as a parameter of regular git.origin (as opposed to only git.github_origin), thereby extending support to GitLab LFS origins (set to enable_lfs = false by default, so change is backwards-compatible to all existing workflows and compatible with non-lfs-enabled Git repositories).

Addresses: #277 and #60

[tardyp]

Hello,
FWIW, I've successfully cherry-picked this and this allowed me to use copybara on a project using lfs (on gitlab)

ping @mikelalcon can you please help merging it?