docs: auto generate pouch cli/api docs via code

[pouchrobot]

Signed-off-by: pouchrobot pouch-dev@alibaba-inc.com

1.Describe what this PR did
This PR is automatically done by AI-based collaborating robot.
Pouchrobot will auto-generate cli/api document via https://github.com/spf13/cobra/tree/master/doc every day.

2.Does this pull request fix one issue?
None

3.Describe how you did it
First, execute command "make client" to build new pouch cli;
Second, execute command "./pouch gen-doc" to generate new cli docs.

For API part, we use a tool swagger2markup to make it.

4.Describe how to verify it
None

5.Special notes for reviews
The cli/api doc must be automatically generated.

[codecov]

Codecov Report

Merging #2401 into master will increase coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2401      +/-   ##
==========================================
+ Coverage    68.4%   68.43%   +0.03%     
==========================================
  Files         271      271              
  Lines       18263    18263              
==========================================
+ Hits        12493    12499       +6     
+ Misses       4347     4343       -4     
+ Partials     1423     1421       -2

Flag	Coverage Δ
#criv1alpha1test	31.72% <ø> (-0.08%)	⬇️
#criv1alpha2test	35.81% <ø> (-0.01%)	⬇️
#integrationtest	39.75% <ø> (+0.03%)	⬆️
#nodee2etest	33.27% <ø> (-0.05%)	⬇️
#unittest	25.51% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
daemon/mgr/snapshot.go	89.85% <0%> (-4.35%)	⬇️
cri/v1alpha2/cri_wrapper.go	60% <0%> (-1.21%)	⬇️
cri/v1alpha2/cri.go	67.81% <0%> (-0.48%)	⬇️
ctrd/container.go	59.28% <0%> (-0.48%)	⬇️
cri/v1alpha2/cri_utils.go	91.09% <0%> (+0.28%)	⬆️
cri/v1alpha1/cri.go	61.03% <0%> (+0.32%)	⬆️
daemon/containerio/container_io.go	75.95% <0%> (+1.09%)	⬆️
pkg/meta/store.go	64.06% <0%> (+1.56%)	⬆️
daemon/mgr/container_utils.go	84.04% <0%> (+1.84%)	⬆️
ctrd/client.go	69.23% <0%> (+2.3%)	⬆️
... and 2 more

[HusterWan]

LGTM