feature: add network prune command

[hellolijj]

Signed-off-by: Junjun Li junjunli666@gmail.com

Ⅰ. Describe what this PR did

add pouch network prune command

Ⅱ. Does this pull request fix one issue?

fix #2213

Ⅲ. Why don't you add test cases (unit test/integration test)? (你真的觉得不需要加测试吗？)

finish it

Ⅳ. Describe how to verify it

$ pouch network prune
WARNING! This will remove all networks not used by at least one container.
Are you sure you want to continue? [y/N]
Deleted Networks:
n1
n2

Ⅴ. Special notes for reviews

[codecov]

Codecov Report

Merging #2897 into master will decrease coverage by 1.88%.
The diff coverage is 81.81%.

@@            Coverage Diff            @@
##           master   #2897      +/-   ##
=========================================
- Coverage   68.88%     67%   -1.89%     
=========================================
  Files         291     290       -1     
  Lines       18249   18251       +2     
=========================================
- Hits        12571   12229     -342     
- Misses       4228    4599     +371     
+ Partials     1450    1423      -27

Flag	Coverage Δ
#criv1alpha2_test	?
#integration_test_0	36.19% <3.03%> (-0.05%)	⬇️
#integration_test_1	35.77% <57.57%> (+0.08%)	⬆️
#integration_test_2	35.97% <45.45%> (-0.2%)	⬇️
#integration_test_3	35.57% <3.03%> (-0.02%)	⬇️
#node_e2e_test	34.11% <3.03%> (-0.1%)	⬇️
#unittest	28.02% <24.24%> (-0.01%)	⬇️

Impacted Files	Coverage Δ
apis/server/router.go	91.56% <100%> (+0.05%)	⬆️
client/network_prune.go	100% <100%> (ø)
apis/server/network_bridge.go	67.56% <75%> (+1.43%)	⬆️
cri/v1alpha2/container_unpause.go	0% <0%> (-81.82%)	⬇️
cri/v1alpha2/container_pause.go	0% <0%> (-81.82%)	⬇️
cri/stream/portforward/httpstream.go	0% <0%> (-70.95%)	⬇️
cri/stream/remotecommand/attach.go	0% <0%> (-64.71%)	⬇️
pkg/meta/errors.go	50% <0%> (-50%)	⬇️
cri/stream/portforward/portforward.go	0% <0%> (-40%)	⬇️
cri/v1alpha2/stream_server.go	42.4% <0%> (-36.81%)	⬇️
... and 23 more

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}