Adding Support for FromEnv properties for Connections

[Sreemoyee26]

We have replaced connection and leaseconnection properties with connectionFromEnv and leaseConnectionFromEnv properties in scalermetadata. Inspite of giving the connection string directly the customer can now specify the environment variable name for connectionFromEnv and give the connection strings as environment variables.

Checklist

• Commits are signed with Developer Certificate of Origin (DCO)
• A PR is opened to update the documentation on our docs repo

Fixes #

• Added connectionFromEnv and leaseConnectionFromEnv as json property name for connection and Leaseconnection.
• Changed the UTs to test this
• Updated the scaledobject yaml files and Demo Project Readme to test out these changes.

[JatinSanghvi]

Please hold before addressing the review comments as we need to think whether to remove support for connection property entirely from the next version of scaler image.

[krishnajaju]

LGTM