Added ability to use raw envrionment variables maps in deployment

[asaf400]

Hello, Internally we use external secret sources,
This PR adds the Ability for the environment variables to reference k8s objects that are per-defined under the pganalyze target namespace by cluster operators.

This solves an issue where a secret that does not conform to either existing methods:

• extraEnv: simple key: value strings
• configMap or secret: injection by using envFrom restricts the data fields conform to target environment variable names

By allowing helm operator to specify raw elements of the env spec of a container, it allows for additional options that are not currently covered.

I do not know how you do versioning for same appVersion patching of the chart-side only changes,
I see that most chart releases correspond to app releases, I ran helm-docs which is the only section in CONTRIBUTING.md that seems relevant for this type of PR

Edits: typo, versioning note