feat: add the K8S mirror proxy setting option

[qinyer]

Signed-off-by: qinyer qy913726062@gmail.com

What type of PR is this?

/kind feature

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #47

Special notes for reviewers:

Does this PR introduced a user-facing change?

1. When you run the KCCTL quick installation script, you can set the KC_REGION environment variable in advance. The script dynamically generates the repo mirror env file based on the value of the variable.
2. Currently supported KC_REGION=cn, then the script automatically sets the third-party repo mirror proxy.
3. Users can set KC_IMAGE_REPO_MIRROR variable to customize the third-party repo mirror proxy.

Additional documentation, usage docs, etc.:

[qinyer]

/assign @x893675

[codecov-commenter]

Codecov Report

Merging #49 (b5d2e92) into master (5310326) will increase coverage by 0.00%.
The diff coverage is 14.28%.

❗ Current head b5d2e92 differs from pull request most recent head 97127d6. Consider uploading reports for the commit 97127d6 to get more accurate results

@@           Coverage Diff           @@
##           master      #49   +/-   ##
=======================================
  Coverage   11.49%   11.49%           
=======================================
  Files          92       92           
  Lines       14217    14224    +7     
=======================================
+ Hits         1634     1635    +1     
- Misses      12366    12372    +6     
  Partials      217      217           

Impacted Files	Coverage Δ
pkg/cli/join/join.go	0.00% <0.00%> (ø)
pkg/scheme/core/v1/k8s/kubeadm.go	1.05% <0.00%> (-0.01%)	⬇️
pkg/scheme/core/v1/k8s/kubeadm_step.go	0.00% <0.00%> (ø)
pkg/cli/deploy/deploy.go	16.15% <100.00%> (+0.12%)	⬆️

[x893675]

/lgtm

[kubeclipper-bot]

LGTM label has been added.

Git tree hash: dc267b0e86f0c4f726adc79510ed8c7adafe2bca

[x893675]

/approve

[kubeclipper-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: qinyer, x893675

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