feat: update VariableScope to add support for prefix

[Pranav2612000]

Why do we need this change?

• We want to extend the VariableScope to accept a prefix. This will allow accessing the VariableList values without needing to pass in the prefix ( for the types which have one )
  For e.g Accessing vault secret using VariableScope.get('secret') when the key in the VariableList is vault:secret.

How does it work?

• We have update the VariableScope to accept a prefix configuration variable in the definition.
• In the constructor, we set the prefix equal to the prefix ( if it exists, default value is '')
• We have updated the get, set, has methods ( and other changes to make them work ) to add/remove the prefix ( fetched from prefix ) from the key, if it exists.