add global nodeSelector, tolerations and affinity

[klamas1]

Description

Added global options nodeSelector, tolerations and affinity. So that you can nail the entire stack to the necessary nodes with a two of lines in values.
Individual settings can still be set for each deployments.

Type of change

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

How has this been tested?

helm upgrade --dry-run

Checklist

• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works

[JannKleen]

@klamas1 I'm not sure if this should be a separate issue, but I think the clickhouse-backup cronjob currently has no nodeSelector at all. Maybe here is a good way to add it?

[klamas1]

@JannKleenI, have added options to charts/posthog/templates/clickhouse-backup-cronjob.yaml

[klamas1]

@guidoiaquinti
I propose to merge this request :)