feat: support mergepatch to envoyproxy/ratelimit deployment

[Xunzhuo]

What type of PR is this?

feat(infra): support mergepatch to envoyproxy/ratelimit deployment

What this PR does / why we need it:

Add unsupported fields in deployment, for private customizations like:

apiVersion: gateway.envoyproxy.io/v1alpha1
kind: EnvoyProxy
metadata:
  name: mergepatch
  namespace: envoy-gateway-system
spec:
  provider:
    type: Kubernetes
    kubernetes:
      envoyDeployment:
        patch:
          type: StrategicMerge
          value:
            spec:
              template:
                spec:
                  hostNetwork: true
                  dnsPolicy: ClusterFirstWithHostNet
---
apiVersion: gateway.networking.k8s.io/v1
kind: GatewayClass
metadata:
  name: eg
spec:
  controllerName: gateway.envoyproxy.io/gatewayclass-controller
  parametersRef:
    group: gateway.envoyproxy.io
    kind: EnvoyProxy
    name: mergepatch
    namespace: envoy-gateway-system

Which issue(s) this PR fixes:

Fixes #2346

[codecov]

Codecov Report

Attention: Patch coverage is 85.71429% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 63.38%. Comparing base (4c79ef9) to head (393da43).
Report is 5 commits behind head on main.

Files	Patch %	Lines
api/v1alpha1/validation/envoyproxy_validate.go	80.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2374      +/-   ##
==========================================
- Coverage   63.38%   63.38%   -0.01%     
==========================================
  Files         119      119              
  Lines       19098    19485     +387     
==========================================
+ Hits        12106    12350     +244     
- Misses       6193     6333     +140     
- Partials      799      802       +3     

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[zirain]

/retest

[Xunzhuo]

/retest

[arkodg]

as a follow up, we need to make sure that if a patch fails, we need to surface that to the EnvoyProxy's GatewayClass status

[arkodg]

should be a pointer since its optional

[arkodg]

small nit, else LGTM !
lets raise a follow up to reuse the same structure for Service as well

[arkodg]

LGTM thanks !
lets raise some follow up GH issues that can hopefully be tackled pre GA

• to populate patch errors in GatewayClass status
• to support patching for envoy.service as well

[shawnh2]

LGTM, thanks for bringing this feature in

[shawnh2]

/retest