feat(kuma-prometheus-sd) add deprecation notice

[austince]

Signed-off-by: austin ce [email protected]

Summary

Having multiple SD mechanisms is causing confusion (see slack thread).
This starts the process of deprecating and removing the old kuma-prometheus-sd adapter.

Full changelog

• Add deprecation log message to kuma-prometheus-sd

Issues resolved

Fix #2852

Documentation

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.
  Could break people's scripts if they are relying on the stdout of kuma-prometheus-sd anywhere, but that seems unlikely / not a true public interface.

[jpeach]

This looks fine to me. @lahabana

[codecov-commenter]

Codecov Report

Merging #2994 (df8c849) into master (09a229c) will increase coverage by 0.06%.
The diff coverage is 55.55%.

@@            Coverage Diff             @@
##           master    #2994      +/-   ##
==========================================
+ Coverage   52.27%   52.33%   +0.06%     
==========================================
  Files         919      919              
  Lines       53000    53007       +7     
==========================================
+ Hits        27705    27742      +37     
+ Misses      23087    23055      -32     
- Partials     2208     2210       +2     

Impacted Files	Coverage Δ
app/kuma-prometheus-sd/cmd/root.go	54.34% <55.55%> (-2.07%)	⬇️
pkg/xds/generator/direct_access_proxy_generator.go	82.75% <0.00%> (-1.15%)	⬇️
api/observability/v1/mads.pb.go	35.56% <0.00%> (+1.03%)	⬆️
pkg/dns/vips_allocator.go	74.00% <0.00%> (+1.33%)	⬆️
pkg/mads/v1/client/client.go	43.75% <0.00%> (+2.50%)	⬆️
pkg/insights/resyncer.go	69.75% <0.00%> (+2.74%)	⬆️
pkg/events/eventbus.go	92.59% <0.00%> (+7.40%)	⬆️
pkg/xds/cache/once/cache.go	94.87% <0.00%> (+7.69%)	⬆️
pkg/core/bootstrap/autoconfig.go	54.46% <0.00%> (+8.03%)	⬆️
pkg/plugins/runtime/gateway/route/sorter.go	71.79% <0.00%> (+10.25%)	⬆️
... and 1 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 09a229c...df8c849. Read the comment docs.

[lahabana]

Makes sense indeed!