docs: auto generate pouch cli/api/contributors 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
We use the following user input CLI document generating command in pouchrobot to generate CLI doc:
go build -o /usr/bin/pouch ./cli; pouch gen-doc

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 #2996 into master will increase coverage by 0.11%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2996      +/-   ##
==========================================
+ Coverage   67.99%   68.11%   +0.11%     
==========================================
  Files         291      291              
  Lines       18660    18660              
==========================================
+ Hits        12688    12710      +22     
+ Misses       4489     4473      -16     
+ Partials     1483     1477       -6

Flag	Coverage Δ
#criv1alpha2_test	34.5% <ø> (-0.05%)	⬇️
#integration_test_0	36.4% <ø> (+0.02%)	⬆️
#integration_test_1	35.43% <ø> (-0.02%)	⬇️
#integration_test_2	36.24% <ø> (-0.15%)	⬇️
#integration_test_3	35.86% <ø> (+0.1%)	⬆️
#node_e2e_test	34.12% <ø> (+0.1%)	⬆️
#unittest	26.68% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
cri/v1alpha2/cri.go	61.33% <0%> (+0.24%)	⬆️
daemon/mgr/container.go	61.08% <0%> (+0.39%)	⬆️
ctrd/container.go	52.78% <0%> (+1.79%)	⬆️
apis/server/utils.go	75% <0%> (+3.84%)	⬆️
ctrd/watch.go	77.92% <0%> (+5.19%)	⬆️

[fuweid]

LGTM