fix: Plugin disable invalid in API /plugin?all=true

[mscb402]

Why submit this pull request?

• Bugfix
• New feature provided
• Improve performance
• Backport patches

What changes will this PR take into?

I tried to disable the plugin in the configuration plugins content of conf.yaml when answering the issue question and it didn't work. After reading the code in the plugin section, I found that in a previously submitted PR #1592, the judgment of whether the plugin is enabled or not was removed. So this PR I fixes the problem and support disabling plugins in conf.yaml plugins.

Related issues

fix/resolve #2735

Checklist:

• Did you explain what problem does this PR solve? Or what new features have been added?
• Have you added corresponding test cases?
• Have you modified the corresponding document?
• Is this PR backward compatible? If it is not backward compatible, please discuss on the mailing list first

[codecov-commenter]

Codecov Report

Merging #2737 (5e41893) into master (4d26409) will decrease coverage by 2.11%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2737      +/-   ##
==========================================
- Coverage   76.40%   74.29%   -2.11%     
==========================================
  Files         139      201      +62     
  Lines        3759     7840    +4081     
  Branches      877      877              
==========================================
+ Hits         2872     5825    +2953     
- Misses        887     1712     +825     
- Partials        0      303     +303     

Flag	Coverage Δ
backend-e2e-test-ginkgo	65.40% <100.00%> (?)
backend-unit-test	50.11% <100.00%> (?)
frontend-e2e-test	76.42% <ø> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
api/internal/handler/schema/plugin.go	100.00% <100.00%> (ø)
api/internal/core/entity/entity.go	90.90% <0.00%> (ø)
api/internal/handler/upstream/upstream.go	86.58% <0.00%> (ø)
api/cmd/root.go	69.56% <0.00%> (ø)
api/internal/core/store/validate.go	71.64% <0.00%> (ø)
api/internal/handler/label/label.go	86.20% <0.00%> (ø)
api/internal/core/migrate/conflict.go	80.00% <0.00%> (ø)
api/internal/utils/consts/api_error.go	50.00% <0.00%> (ø)
api/internal/core/storage/etcd.go	54.38% <0.00%> (ø)
api/internal/core/server/http.go	56.52% <0.00%> (ø)
... and 54 more

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[mscb402]

@bzp2010 @tokers do you have time help me to review this