feat: support plugins field in ApisixConsumer

[AlinsRan]

Summary

Add a generic plugins field to ApisixConsumerSpec so that consumer-scoped plugins (e.g. limit-count, limit-req) can be attached to an ApisixConsumer resource directly, without being limited to the auth plugins exposed through authParameter.

Changes

• ApisixConsumerSpec gains a Plugins []ApisixRoutePlugin field, following the same pattern as ApisixRoute and ApisixGlobalRule. Enabled plugins are merged after the auth plugin derived from authParameter; an enabled plugin with the same name takes precedence.
• authParameter is now optional (omitempty). Both authParameter and plugins are optional at the API level; the controller handles the case where neither is set.
• Translator updated to process the new Plugins slice via the existing buildPluginConfig helper.
• Controller and indexer extended to load and index Secrets referenced by spec.plugins[].secretRef, consistent with ApisixRoute and ApisixGlobalRule behavior.
• deepcopy updated for the new Plugins slice and now-optional AuthParameter pointer (auto-generated by make generate).
• E2e tests added for two scenarios:
  • authParameter + extra plugins (e.g. limit-count rate limiting at consumer level)
  • plugins only — no authParameter (e.g. key-auth configured directly via plugins)

Example

apiVersion: apisix.apache.org/v2
kind: ApisixConsumer
metadata:
  name: my-consumer
spec:
  ingressClassName: apisix
  authParameter:
    keyAuth:
      value:
        key: my-secret-key
  plugins:
  - name: limit-count
    enable: true
    config:
      count: 100
      time_window: 60
      rejected_code: 429
      policy: local

Or, using plugins only (without authParameter):

apiVersion: apisix.apache.org/v2
kind: ApisixConsumer
metadata:
  name: key-auth-consumer
spec:
  ingressClassName: apisix
  plugins:
  - name: key-auth
    enable: true
    config:
      key: my-secret-key

[shreemaan-abhishek]

shouldn't we support multi-auth too?

[AlinsRan]

The purpose of this PR is to support plugins.
multi-auth can still be configured through plugins.