feat!: Add support for FromEnv properties for connections

[Sreemoyee26]

This PR replaces the connection and leaseConnection properties in the scaler metadata with connectionFromEnv and leaseConnectionFromEnv respectively. Instead of directly passing the connection string, user will be required to specify the name of the environment variable in the scale target container's environment that contains the Cosmos DB connection string.

Checklist

• Commits are signed with Developer Certificate of Origin (DCO)

Fixes

• Added new JSON properties: connectionFromEnv and leaseConnectionFromEnv in the scaler metadata.
• Updated the unit tests accordingly.
• Updated the scaled object 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