Ceph CSI v2.1.0 Release

Release Issue #806

Changelog or Highlights:

Features:

Add support for rbd static PVC
Move cephfs subvolume support from `Alpha` to `Beta`.
Added support for rbd topology-based provisioning.
Support externally managed configmap.
Updated Base image to ceph Octopus
Added csiImageKey to keep track of the image name in RADOS omap
Added E2E for helm charts
...

Enhancements:

Implement CreateVolume with go-ceph which boosts performance.
Migrated from `dep` to `go modules`
Updated Kubernetes version to v1.18.0
Updated golang version to 1.13.9
Updated Kubernetes sidecar containers to latest version
E2E: Add Ability to test with non root user
...

Bug Fixes:

Log an error message if cephfs mounter fails during init
Aligned with klog standards for logging
Added support in to run E2E in a different namespace
Removed cache functionality for cephfs plugin restart
rbd: fallback to inline image deletion if adding it as a task fails
code cleanup for static errors and unwanted code blocks
Fix mountoption issue in  rbd
travis: re-enable running on arm64
...

Deprecated:

GRPC metrics in cephcsi

Documentation:

Added Document to cleanup stale resources
Updated ceph-csi support matrix
dev-guide: add reference to required go-ceph dependencies
Update upgrade doc  for node hang issue
....