fix: Add client-go QPS and Burst overrides in code and helm chart

[grzesuav]

fixes ##996

What does this PR do?

• Adds new functionality
• Alters existing functionality
• Fixes a bug
• Improves documentation or testing

Please briefly describe your changes as well as the motivation behind them:

• Adds posibility to override default client-go QPS and Burst, both in controller code and helm chart

Code Quality Checklist

• The documentation is up to date.
• My code is sufficiently commented and passes continuous integration checks.
• I have signed my commit (see Contributing Docs).

Testing

• I leveraged continuous integration testing
  • by depending on existing unit tests or end-to-end tests.
  • by adding new unit tests or end-to-end tests.
• I manually tested the following steps:
  • x
  • locally.
  • as a canary deployment to a cluster.

[aymericDD]

These client-go rate limiting flags should be moved to the configuration system in config/config.go for consistency. Yhey're defined separately in main.go but
should follow the same pattern as other controller settings - being part of the controllerConfig struct with viper binding support for config files and ConfigMap
overrides.

1. Add to controllerConfig struct (config/config.go:34-60):

  type controllerConfig struct {
        HealthProbeBindAddr              string                          `json:"healthProbeBindAddr" yaml:"healthProbeBindAddr"`
        MetricsBindAddr                  string                          `json:"metricsBindAddr" yaml:"metricsBindAddr"`
        MetricsSink                      string                          `json:"metricsSink" yaml:"metricsSink"`
        // Add these two fields:
        ClientGoQPS                      float64                         `json:"clientGoQps" yaml:"clientGoQps"`
        ClientGoBurst                    int                             `json:"clientGoBurst" yaml:"clientGoBurst"`
        ExpiredDisruptionGCDelay         time.Duration                   `json:"expiredDisruptionGCDelay" yaml:"expiredDisruptionGCDelay"`
        // ... rest of fields
  }

2. Add flag binding in New() function (similar to existing patterns around line 139):

  mainFS.Float64Var(&cfg.Controller.ClientGoQPS, "client-go-qps", 20, "Number of queries per second client-go is allowed to make (default 20)")

  if err := viper.BindPFlag("controller.clientGoQps", mainFS.Lookup("client-go-qps")); err != nil {
        return cfg, err
  }

  mainFS.IntVar(&cfg.Controller.ClientGoBurst, "client-go-burst", 30, "Allowed burst queries for client-go (default 30)")

  if err := viper.BindPFlag("controller.clientGoBurst", mainFS.Lookup("client-go-burst")); err != nil {
        return cfg, err
  }

3. Remove from main.go and use config values:

  // Remove from main.go:
  // clientGoQPS   = flag.Float64("client-go-qps", 20, "...")
  // clientGoBurst = flag.Int("client-go-burst", 30, "...")

  // Use in client initialization:
  // *clientGoQPS -> cfg.Controller.ClientGoQPS
  // *clientGoBurst -> cfg.Controller.ClientGoBurst

This way, these settings can be configured via YAML files, ConfigMaps, and environment variables just like all other controller settings.