Make Concierge server port numbers configurable

[cfryanr]

Make several ports configurable to partially address #864.

• Add aggregatedAPIServerPort to the Concierge's static ConfigMap
  • The aggregated API server now defaults to port 10250 to allow it to work without needing further configuration on private GKE clusters.
• Add impersonationProxyServerPort to the Concierge's static ConfigMap (still defaults to 8444 as before)
• Allow both port numbers to be configured to any value within the range 1024 to 65535. It cannot be below 1024 because the container is not running as root.
• This does not include adding new config knobs to the ytt values file, so while it is possible to change this port without needing to recompile, it is not convenient. This is because it is unlikely that users would need to configure this, and we are waiting for more feedback before promoting it to a first-class configuration option.

Release note:

Makes it possible to change the listening port numbers of the aggregated API server and impersonation proxy, which is typically not necessary but could be used for example on a cluster using host networking where these ports are already consumed by other services. The aggregated API server now defaults to port 10250 to allow it to work without needing further configuration on private GKE clusters.

[codecov]

Codecov Report

Merging #888 (f28b33b) into main (537f852) will increase coverage by 0.04%.
The diff coverage is 88.00%.

@@            Coverage Diff             @@
##             main     #888      +/-   ##
==========================================
+ Coverage   78.94%   78.99%   +0.04%     
==========================================
  Files         132      132              
  Lines        9491     9510      +19     
==========================================
+ Hits         7493     7512      +19     
+ Misses       1745     1744       -1     
- Partials      253      254       +1     

Impacted Files	Coverage Δ
internal/concierge/server/server.go	26.61% <0.00%> (-0.44%)	⬇️
internal/config/concierge/config.go	90.36% <100.00%> (+2.30%)	⬆️
...ntroller/impersonatorconfig/impersonator_config.go	93.42% <100.00%> (+0.01%)	⬆️
...l/localuserauthenticator/localuserauthenticator.go	57.20% <0.00%> (+0.93%)	⬆️

---

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 537f852...f28b33b. Read the comment docs.