LAKITU: Add retry logic in git-r3 eclass

Add retry logic in git-r3 eclass in order to reduce the transient error at runtime. go/cos-rev/28982 added retry logic in git-2 but git-r3 is also used at some places. So, it's good to have retry logic while fetching repo in git-r3.

BUG=b/195965589
TEST=presubmit
RELEASE_NOTE=None

Reviewed-on: https://cos-review.googlesource.com/c/third_party/overlays/eclass-overlay/+/29207
Reviewed-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Tested-by: Rayan Dasoriya <dasoriya@google.com>
Change-Id: I263ecd887575199d18a4a430b498fa14f4dd4db5
Reviewed-on: https://cos-review.googlesource.com/c/third_party/overlays/eclass-overlay/+/29662
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>