feat(CLI): Support debug command

[gaocegege]

Description

We need to support debug commands to help users debug the build artifact easily.

Use case

Users may encounter problems during the build process. And the error is hard to resolve since the build process is complex.

As the envd user, I want to get the failed build artifact running, thus I can debug it in the running environment to know why it fails.

Ref https://github.com/ktock/buildg

[gaocegege]

Some references:

• Support interactive frontend (initial support towards pluggable debugger) moby/buildkit#2835
• Support launching shell on a build step for debugging moby/buildkit#2813
• Improved debugging support moby/buildkit#1472
• Add --invoke option to launch a container from the build result docker/buildx#1168
• Add Exec to the gateway API. moby/buildkit#749
• Proposal: build debugging in buildx (interactive sessions) docker/buildx#1104

[aseaday]

https://github.com/ktock/buildg seems a good option.

[aseaday]

IMO, envd manifest shoud be a statement of final environment rather than the build process. So I think this issue's priority is not as important as others. Envd users only write out what they need.

[gaocegege]

@aseaday Could you please explain more about it?

[gaocegege]

This command is used to debug why the image fails to build. For example:

def build():
     install.conda_packages(name = [
        "un-existed",
    ], channel= ["pytorch"])
    base(os="ubuntu20.04", language="python3.8")

$ envd build
err: ...
(envd-debug) > exec bash
$ # Debug here.