feat(context): Support unix context and daemonless

[gaocegege]

Fix #1056

This PR adds two new image tensorchord/envd-from-scratch built by goreleaser, and tensorchord/envd built by the build.sh.

Users can use tensorchord:envd to run build daemonlessly:

docker run \                                                        
    -it \                                                                                       
    --rm \                                                                                      
    --security-opt seccomp=unconfined \                                                         
    --security-opt apparmor=unconfined \                                                        
    -e BUILDKITD_FLAGS=--oci-worker-no-process-sandbox \                                        
    --entrypoint /envd-daemonless.sh \                                                          
    -v /home/gaocegege/code/go/src/github.com/tensorchord/envd/examples/python-basic:/tmp/work t
ensorchord/envd:daemonless-rootless --debug build -p /tmp/work --output type=image,name=test   

[VoVAllen]

LGTM. What's the advantage of daemonless?

[gaocegege]

LGTM. What's the advantage of daemonless?

As @Xiaoaier-Z-L said, there is no need to launch a buildkitd deployment on Kubernetes. We can just create a job to build envd image.

[gaocegege]

Comments addressed, PTAL.

[kemingy]

/lgtm

[muniu-bot]

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