fix(core): new pathway to apply namespace targeted decorators

[sanketshevkar]

Closes #874

Changes

• Introduce new feature flag accessed using optional parameters and as environment variable to enable new pathway
• When flags disabled, namespace targeted dcs would be get applied to all declarations within a namespace and if enabled just on top of the namespace.
• A new warning emitter pattern introduced to emit deprecation warning.

Flags

Screenshots or Video

Related Issues

• Issue DCS with namespace target, don't apply decorators on top of the namespace. #874

Author Checklist

• Ensure you provide a DCO sign-off for your commits using the --signoff option of git commit.
• Vital features and changes captured in unit and/or integration tests
• Commits messages follow AP format
• Extend the documentation, if necessary
• Merging to main from fork:branchname

[dselman]

Concerto-Core needs to be usable within the web browser.