Add nodeSelector and tolerations config for all pods of Helm chart

[stevenstetzler]

This PR is meant to fix #1130

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[consideRatio]

This PR is related to, but does not fix #1486, which should be fixed in a separate PR.

[consideRatio]

Thank you @stevenstetzler for getting this started ❤️ 🎉! I made some adjustments to: a) align configuration with other chart configuration, b) test this with dummy values in our linting script, and c) document this configuration in schema.yaml.

It would be reasonable to have a chart wide nodeSelector/nodeAffinity for core pods to some predefined label, and we already intend to have that, but we need to implement it correctly first - this is issue #1486.

It would also be reasonable to have a similar chart wide toleration of some taint for core pods, but I don't want to push for that unless its clearly wanted by multiple people as it would add quite a bit of complexity as usual - mostly because augmenting values in Helm templates is a mess, and deprecations etc will make it become a terrible blob of code to maintain.

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