chore(kuma-cp) remove dp token from xds metadata

[jakubdyszkiewicz]

Summary

Remove DP token from XDS Metadata since it's not needed anymore.
It was used when secrets were served over separate SDS connections.

Issues resolved

No issues.

Documentation

• No docs.

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 #3282 (5ab9f21) into master (96b6efd) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3282      +/-   ##
==========================================
+ Coverage   52.38%   52.40%   +0.01%     
==========================================
  Files         927      927              
  Lines       54066    54059       -7     
==========================================
+ Hits        28320    28327       +7     
+ Misses      23526    23512      -14     
  Partials     2220     2220              

Impacted Files	Coverage Δ
pkg/core/xds/metadata.go	62.66% <ø> (-0.30%)	⬇️
pkg/xds/bootstrap/template_v3.go	99.12% <ø> (-0.01%)	⬇️
pkg/core/runtime/component/component.go	81.13% <0.00%> (-7.55%)	⬇️
pkg/core/resources/manager/cache.go	83.11% <0.00%> (-5.20%)	⬇️
api/observability/v1/mads.pb.go	35.56% <0.00%> (+1.03%)	⬆️
pkg/xds/generator/direct_access_proxy_generator.go	83.90% <0.00%> (+1.14%)	⬆️
pkg/dns/vips_allocator.go	74.50% <0.00%> (+1.30%)	⬆️
pkg/mads/v1/client/client.go	43.75% <0.00%> (+2.50%)	⬆️
pkg/insights/resyncer.go	69.89% <0.00%> (+2.67%)	⬆️
pkg/events/eventbus.go	92.59% <0.00%> (+7.40%)	⬆️
... and 1 more

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[bartsmykla]

lgtm