add nydus container image service

The nydus project designs and implements an user space filesystem on top of
a container image format that improves over the current OCI image
specification. Its key features include:
* Container images are downloaded on demand
* Chunk level data duplication
* Flatten image metadata and data to remove all intermediate layers
* Only usable image data is saved when building a container image
* Only usable image data is downloaded when running a container
* End-to-end image data integrity
* Compactible with the OCI artifacts spec and distribution spec
* Integrated with existing CNCF project dragonfly to support image distribution in large clusters
* Different container image storage backends are supported

The initial commits include:
* A `nydusify` tool to convert an OCI format container image into a nydus format container image
* A `nydus-image` tool to convert an unpacked container image into a nydus format image
* A `nydusd` daemon binary to read a nydus format image and expose a FUSE mountpoint for containers to access

Signed-off-by: yansong.ys <[email protected]>
Signed-off-by: Changwei Ge <[email protected]>
Signed-off-by: Liu Bo <[email protected]>
Signed-off-by: Liu Jiang <[email protected]>
Signed-off-by: henry.hj <[email protected]>
Signed-off-by: Eric Ren <[email protected]>
Signed-off-by: jihui.xjh <[email protected]>
Signed-off-by: Peng Tao <[email protected]>

Author: bergwolf

.gitignore

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