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 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 #2830 into master will increase coverage by 1.89%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2830      +/-   ##
==========================================
+ Coverage   67.27%   69.16%   +1.89%     
==========================================
  Files         279      279              
  Lines       17603    17603              
==========================================
+ Hits        11842    12175     +333     
+ Misses       4429     4049     -380     
- Partials     1332     1379      +47

Flag	Coverage Δ
#criv1alpha2_test	39.38% <ø> (ø)	⬆️
#integration_test_0	36.36% <ø> (-0.02%)	⬇️
#integration_test_1	35.22% <ø> (?)
#integration_test_2	36.43% <ø> (+0.05%)	⬆️
#integration_test_3	35.25% <ø> (-0.01%)	⬇️
#node_e2e_test	35.07% <ø> (-0.04%)	⬇️
#unittest	28.69% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
apis/server/utils.go	71.15% <0%> (-3.85%)	⬇️
cri/v1alpha2/cri.go	69.06% <0%> (ø)	⬆️
apis/server/router.go	91.35% <0%> (+0.61%)	⬆️
daemon/mgr/spec_linux.go	79.15% <0%> (+0.7%)	⬆️
daemon/mgr/container_storage.go	60.24% <0%> (+0.81%)	⬆️
ctrd/container.go	54.64% <0%> (+1.13%)	⬆️
registry/auth.go	55.14% <0%> (+1.86%)	⬆️
ctrd/image.go	69.96% <0%> (+1.9%)	⬆️
pkg/utils/utils.go	83.26% <0%> (+2.04%)	⬆️
apis/server/volume_bridge.go	87.17% <0%> (+2.56%)	⬆️
... and 16 more

[allencloud]

LGTM