fix(kuma-cp): protocol check should be case insensitive

[lukidzi]

Summary

When protocol label is defined with uppercased value TCP deployment of gateway fails because it's different than TCP.
We can discuss in issue if we want this way or maybe make it different way.

Full changelog

• [Implement case insensitive comparision]
• [added to log information about provided protocol]

Issues resolved

Fix #4247

Documentation

• Link to the website documentation PR

Testing

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

Backwards compatibility

• Update UPGRADE.md with any steps users will need to take when upgrading.
• Add backport-to-stable label if the code follows our backporting policy

[jakubdyszkiewicz]

do we also treat kuma.io/protocol as case insensitive down the road when we actually use it? Somewhere around outbound_proxy_generator.go etc.

[lukidzi]

In some places, we check lower cases by using https://github.com/kumahq/kuma/blob/master/pkg/core/resources/apis/mesh/dataplane_helpers.go#L26. Maybe the best option will be to lowercase that at inbound_converter.

[jakubdyszkiewicz]

I'm ok with lower-casing in inbound converter

[lahabana]

Decision from triage:

• Should not touch casing in validation (except fixing error message).
• In inbound_converter.go should lower case appProtocol/annotation.

[codecov-commenter]

Codecov Report

Merging #4248 (a01b4a2) into master (cc164cd) will decrease coverage by 0.05%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #4248      +/-   ##
==========================================
- Coverage   55.65%   55.60%   -0.06%     
==========================================
  Files         935      935              
  Lines       56347    56347              
==========================================
- Hits        31361    31331      -30     
- Misses      22504    22523      +19     
- Partials     2482     2493      +11     

Impacted Files	Coverage Δ
...kg/core/resources/apis/mesh/dataplane_validator.go	100.00% <100.00%> (ø)
...ugins/runtime/k8s/controllers/inbound_converter.go	89.38% <100.00%> (ø)
pkg/clusterid/creator.go	73.33% <0.00%> (-13.34%)	⬇️
pkg/metrics/store/counter.go	74.54% <0.00%> (-10.91%)	⬇️
pkg/core/runtime/component/component.go	82.45% <0.00%> (-10.53%)	⬇️
pkg/core/tokens/default_signing_key.go	66.66% <0.00%> (-5.56%)	⬇️
...s/authn/api-server/tokens/admin_token_bootstrap.go	82.00% <0.00%> (-4.00%)	⬇️
pkg/defaults/components.go	82.14% <0.00%> (-3.58%)	⬇️
pkg/core/secrets/manager/global_manager.go	39.39% <0.00%> (-3.04%)	⬇️
pkg/core/resources/manager/cache.go	85.71% <0.00%> (-2.60%)	⬇️
... and 3 more

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