Fetch and filter blobs

Overview

Based on the work in #427043 (closed), this issue focus on improving the implementation of the push check introduced in #427039 (closed), such that:

• We only fetch blobs under a certain size limit from Gitaly (see this internal discussion).
• We dismiss any blobs that are binary (by checking for their binary attribute).
• We make sure to only return new blobs when a quarantine directory is present.

Please see parent epic for more details and considerations.

Prerequisites

• Determine blob size limit to use as a threshold.

Implementation Plan

• Update the new push check to:
  • Fetch blobs under a certain size limit by passing bytes_limit to gRPC calls list_blobs and list_all_blobs.
  • Remove blobs that are binary from the array of blobs fetched.
  • Ensure only new blobs are returned if a quarantine directory is present (see discussion).