separate nodeSelector for metrics-agg

Proposed changes

Existing implementation assumes that the metrics daemonset and the metrics-agg will requirement the same nodeSelector configuration.

However, this may not always be the case. For example, I want to keep management workloads on a set of management nodes. The metrics-agg deployment will count as a management workload. However, I still want to have the metrics daemonset running on all my nodes to collect metrics. With the current template this is not possible and the .Values.nodeSelector is common for both the metrics daemonset and the metrics-agg deployment.

This update implements a separate aggregatorNodeSelector value to make it distinct from the orignal nodeSelector value.

This fixes: https://github.com/splunk/splunk-connect-for-kubernetes/issues/776

Types of changes

What types of changes does your code introduce? Put an x in the boxes that apply

[x] Bugfix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

Put an x in the boxes that apply.

[x] I have read the CONTRIBUTING doc
[x] I have read the CLA
[x] I have added necessary documentation (if appropriate)
[x] Any dependent changes have been merged and published in downstream modules

splunk / splunk-connect-for-kubernetes