fix parsing of grafana feature flags that're enabled via the feature_toggles.enabled syntax

[joeyorlando]

What this PR does

Grafana provides two methods for enabling feature flags:

• feature_toggles.enabled
• feature_toggles.<name_of_feature_flag>

For example, to enable accessControlOnCall you could either do:

{
  "feature_toggles": {
    "enabled": "accessControlOnCall,someOtherCoolFeatureFlag"
  }
}

or:

{
  "feature_toggles": {
    "accessControlOnCall": true,
    "someOtherCoolFeatureFlag": true
  }
}

In method 1, if they're multiple feature flags present, they are comma separated, not space separated. This PR fixes this parsing issue.

Checklist

• Unit, integration, and e2e (if applicable) tests updated
• Documentation added (or pr:no public docs PR label added if not required) (N/A)
• CHANGELOG.md updated (or pr:no changelog PR label added if not required)