Validation modification on cd pipeline creation - One cd per environment

[vikramdevtron]

Summary

Gitops is mandatory for devtron apps, make this an optional. without gitops configuration user can create and deploy application.

Validate single cd pipeline per environment. Check must be common for helm type and acd type pipeline, if helm app already exists in same environment then stop for creating new one.

Motivation

Make devtron easy for users who are facing difficulties in configuring GITOPS.

Proposal

Story scope & estimation

https://docs.google.com/document/d/14YmjJKm8wdlUTjj5nknx9FQjd8NCDwtiTbbu45Rxd5c/edit#heading=h.jnwn9sf60ziz

Testing Guideline [Optional]

[vikramdevtron]

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