Enable partial clone with blob size filter by default

Problem to solve

Once it is possible to enable blob and sparsity filters independently, we should enable blob filters by default since they are low risk and make it easy for customers to try out partial clone.

Proposal

Currently we have one feature flag gitaly_upload_pack_filter to control both blob and sparsity filters.

• reuse the existing feature flag gitaly_upload_pack_filter for blob filters, and default to enabled
• create a new feature flag gitaly_upload_pack_filter_sparsity for sparsity filters, and default to false

Links/references