feat: support stack name input

[TheOrangePuff]

Description of the proposed changes

• There are situations where we may not want to specify the environment variable for STACK_NAME. E.g. here: https://github.com/aligent/aligent-aws-access-cdk I need to deploy two stacks to the same environment. I don't really want to create two different environments just for one variable each 😅 I think this is cleaner.

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