gwctl: Show Events, Analysis and few other fields for various resources.

[gauravkghildiyal]

What type of PR is this?
/kind feature

What this PR does / why we need it:

This PR addresses missing information in the display of various resources and
enhances the presentation of printed information. After this and the related
issue #3037 get completed, all gwctl describe views will have the relevant
information and some visual appeal.

Examples:

$ gwctl describe backends

  ...
  (truncated)
  ...
  ReferencedByRoutes:
    Kind       Name
    ----       ----
    HTTPRoute  default/grpc-httproute
    HTTPRoute  default/grpc-httproute-2
  DirectlyAttachedPolicies:
    Type                                 Name
    ----                                 ----
    HealthCheckPolicy.networking.gke.io  default/grpc-gateway-healthcheck
  EffectivePolicies:
    default/grpc-gateway:
      HealthCheckPolicy.networking.k8s.io:
        default:
          checkIntervalSec: 15
          config:
            http2HealthCheck:
              port: 1234
              portSpecification: USE_FIXED_PORT
            type: HTTP2
          healthyThreshold: 1
          logConfig:
            enabled: true
          timeoutSec: 15
          unhealthyThreshold: 2
  Events:
    Type    Reason  Age  From                   Message
    ----    ------  ---  ----                   -------
    Normal  SYNC    36h  sc-gateway-controller  SYNC on default/grpc-svc was a success

$ gwctl describe gateway

  ...
  (truncated)
  ...
  AttachedRoutes:
    Kind       Name
    ----       ----
    HTTPRoute  default/grpc-httproute-2
  DirectlyAttachedPolicies: <none>
  Analysis:
  - Gateway "default/random-gateway" references a non-existent GatewayClass "random"
  Events:
    Type    Reason  Age  From                   Message
    ----    ------  ---  ----                   -------
    Normal  SYNC    36h  sc-gateway-controller  SYNC on default/grpc-gateway-2 was a success

Which issue(s) this PR fixes:

Closes a couple of items from #2761
Fixes #2994

Does this PR introduce a user-facing change?:

Show Events and Analysis when describing resources.

[youngnick]

/lgtm

[youngnick]

/hold for other review though

[gauravkghildiyal]

(Rebased)

[mlavacca]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gauravkghildiyal, mlavacca

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• gwctl/OWNERS [gauravkghildiyal]

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[gauravkghildiyal]

Thanks for the review, both! (I'll unhold based on the two reviews)

/unhold