CP/DP Split: Remove NGINX manager and deployment

[sjberman]

Removing the nginx runtime manager and deployment container since nginx will live in its own pod managed by agent. Temporarily saving the nginx deployment and service for future use.

Updated the control plane liveness probe to return true once it's processed all resources, instead of after it's written config to nginx (since nginx may not be started yet in the future architecture).

Testing: Verified that the control plane is able to start and run on its own.

Closes #2838

[codecov]

Codecov Report

Attention: Patch coverage is 31.37255% with 35 lines in your changes missing coverage. Please review.

Project coverage is 90.50%. Comparing base (06fd179) to head (b7d53db).

Files with missing lines	Patch %	Lines
internal/mode/static/manager.go	0.00%	25 Missing ⚠️
internal/mode/static/nginx/agent/agent.go	0.00%	7 Missing ⚠️
internal/mode/static/handler.go	81.81%	1 Missing and 1 partial ⚠️
cmd/gateway/initialize.go	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                         Coverage Diff                         @@
##           change/control-data-plane-split    #2936      +/-   ##
===================================================================
+ Coverage                            89.93%   90.50%   +0.56%     
===================================================================
  Files                                  111      105       -6     
  Lines                                11421    10979     -442     
  Branches                                50       50              
===================================================================
- Hits                                 10271     9936     -335     
+ Misses                                1089      990      -99     
+ Partials                                61       53       -8     

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[kate-osborn]

See my review for a small nit, but otherwise LGTM

[salonichf5]

nit: I see comments in various places using we've or we are ready. Do you think it would be better to use control plane or NGINX Gateway Fabric to be clearer for future readers?

[sjberman]

nit: I see comments in various places using we've or we are ready. Do you think it would be better to use control plane or NGINX Gateway Fabric to be clearer for future readers?

I don't feel strongly about the wording in this case