New function to negate expressions

[Shobhit21287]

Closes #13966

Added a negate function for expr.Expr letting users negate expressions of type float, Uint, duration.

The following have been done

• A new unary operator introduced
• relevant tests have been modified and a few new ones have been added
• Release note has been added

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[aaryav-3]

hi @Shobhit21287 , thank you so much for your contribution! there is a small typo in this line, should be Example*

Also, perhaps you should leave a new line at the end of the release note, are the docs still compiling?

[aaryav-3]

I think Uint here may be problematic and can lead to undefined or unexpected behavior, because unsigned integers cannot represent negative values (a user expecting a signed integer or an error may end up getting back a large unsigned integer (2**3) - value which is an ambiguous value, and a silent failure). While negation is unambiguous for Float and Duration, negating a Uint requires choosing a specific interpretation like 2's complement, to negate which, a specialized method may need to be defined.

So for now, perhaps Uint could be removed from the check, or specialized logic can be added? Do let me know what you think! Thank you

[aaryav-3]

Hi @Shobhit21287 , this work is a great addition to qiskit, your PR is well written and clean. I had just some clarifications before it looks good to go