feat(helm): deprecated prerequisites chart and added init containers

[justmike1]

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable)

Context

REOPEN OF #294

Being dependent on another helm chart and using helm hooks for proper deployment making introduces number of issues, for example:

• google marketplace uses helm charts for templates and then kubectl one by one, which makes using this chart for it impossible.

• if a user deploys prerequisites without the --wait flag (like in the docs) and doesn't wait for deployments to finish and straight away deploys datahub, the pods will continually restart until ready.

• GMS authentication breaks datahub-system-update-job #265

• Many more tools that doesn't support helm hooks while using helm for packaging templates per services

The change

I introduce the same methodology of dependent deployments but with init containers, they will check if the needed service is ready before initiating the main pod

TESTS

You can use this repository meanwhile to test this feature

Notes

• Included PR updated postgresql #290
• nocode migrations auto detect SQL platform
• Added ability to disable cronJobs as I have experienced problems with their deletions building google marketplace application

TODO

• update docs

Maintenance

I will continue maintaining and improve the chart, but this is a good init start, I don't want this PR to be a too major change unrelated to the goal (which is one helm chart for all).

[justmike1]

can someone tell me if this is too big of a PR? I can just add initContainers and give the ability to disable helmhooks like I did in superset