[Testing] Expand embedding tests for all operators

[jpmoutinho]

Describe the feature

We should have more comprehensive tests for correctness of the Embedding class.

The tests should include:

• Testing every gate
• Testing every composite gate (Sequence, Add, Scale)
• Testing the run method (the sample and expectation use the run anyway)
• Testing the expectation method for an observable with embedded parameters
• Testing the tensor method

It should be implemented because

No response

Additional context

No response

Would you like to work on this issue?

Yes