Revamp ChebyshevPolynomial

[charlesyuan314]

• Migrate ChebyshevPolynomial to the modern BlockEncoding interface by changing the base class, attribute type, and signature.
• Clarify in the docstring that ChebyshevPolynomial only works correctly with block encodings $\mathcal{B}[A]$ of Hermitian matrices $A$.
• Make ChebyshevPolynomial correct for use with non-Hermitian block encodings $\mathcal{B}[A] \neq \mathcal{B}[A]^\dagger$, following the existing reference.

The last change involves invoking $\mathcal{B}[A]^\dagger$. Most of our block encodings are not Hermitian, making this necessary for correctness. The total number of invocations of $\mathcal{B}[A]$ and its adjoint remains equal to the specified order of the Chebyshev polynomial.

There are no existing users of ChebyshevPolynomial to update.

[fdmalone]

Nice!