fix: unique registration action for each createThunk instance

[VldMrgnn]

This PR introduces a test to verify that the API is called only once, even if it is registered twice.
It also suggests a solution by checking for the existence of the signal before registering it.
I am not fully certain about the deeper implications of this change, and further reviews are certainly needed.

[VldMrgnn]

Concept: Unique Actions for a Unique Register

1. Every time createThunks() is called, we generate a unique instanceId to identify each thunk instance.

2. To ensure idempotency, we use a registrationMap that tracks whether each createThunks instance has been registered. This check and registration happen in the function* register().

3. The main idea is to create a unique registration action for each createThunks instance. Instead of using a generic action like ${API_ACTION_PREFIX}REGISTER_THUNK, we use a distinctive action like ${API_ACTION_PREFIX}REGISTER_THUNK_${instanceId}. This ensures each thunk instance gets its own watcher, which listens only for its specific registration action.

[VldMrgnn]

I will close this PR and open a new one with a clean branch that contains only the relevant changes. Thanks for your patience!