feat(kuma-cp) Intermediate CA support

[jakubdyszkiewicz]

Summary

Introduce support for Intermediate CA in Provided backend.

Full changelog

• Remove CA validators
• Add Intermediate CA test

Issues resolved

Fix #759

Documentation

• docs(policies) intermediate CA kuma-website#506

Testing

• Unit tests
• E2E tests
• Manual testing on Universal
• Manual testing on Kubernetes

Backwards compatibility

• Add backport-to-stable label if the code is backwards compatible. Otherwise, list breaking changes.

[codecov-commenter]

Codecov Report

Merging #2575 (889b49d) into master (fbd0831) will decrease coverage by 0.03%.
The diff coverage is 15.29%.

@@            Coverage Diff             @@
##           master    #2575      +/-   ##
==========================================
- Coverage   52.68%   52.65%   -0.04%     
==========================================
  Files         867      868       +1     
  Lines       48270    48336      +66     
==========================================
+ Hits        25433    25453      +20     
- Misses      20783    20828      +45     
- Partials     2054     2055       +1     

Impacted Files	Coverage Δ
test/e2e/mtls/universal/mtls_backends.go	0.00% <0.00%> (ø)
pkg/plugins/ca/provided/ca_cert_validator.go	88.00% <81.25%> (-1.29%)	⬇️
pkg/core/resources/manager/cache.go	84.41% <0.00%> (+2.59%)	⬆️
app/kumactl/cmd/root.go	73.68% <0.00%> (+3.50%)	⬆️
pkg/plugins/resources/memory/store.go	82.06% <0.00%> (+4.34%)	⬆️
pkg/core/bootstrap/autoconfig.go	54.46% <0.00%> (+8.03%)	⬆️
pkg/core/resources/store/customizable_store.go	88.88% <0.00%> (+11.11%)	⬆️

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[lahabana]

That was easy to add :)