[TASK] Create deprecation warning for mandating existingSecrets (removes need for secrets extraction during upgrade)

[jessesimpson36]

Related to

https://github.com/camunda/distribution/issues/125

Epic:
https://github.com/camunda/product-hub/issues/1957

Overview

As part of the Epic to improve the upgrade experience, we believe upgrading will be simpler by removing the auto-generation of passwords, and instead move to specifying the passwords in Secrets.

This task is to create a constraint with a few different modes:

1. Deprecation warning: some sort of alert that will inform the user that in the next minor version, an error will appear if you do not specify existingSecrets for all passwords
2. Deprecation error: if existingSecrets are not present, prevent the installation from finishing.

[jessesimpson36]

Related to
#403