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Improve casting and error message for `ParameterExpression` (#10244)

* Improve casting and error message for `ParameterExpression`

Previously, we assumed that the only reason a cast of
`ParameterExpression` to `complex`/`float`/`int` could fail was because
of unbound parameters, and emitted an error accordingly.  This is not
the case; a fully bound complex value will still fail to convert to
`float`.

This PR improves the error messages in these cases, and works around a
difference of Sympy and Symengine, where the latter will fail to convert
real-valued expressions that were symbollically complex at some point in
their binding history to `float`.  Sympy more reliably reduces values
down to real-only values when the imaginary part is exactly cancelled,
which is a use-case our users tend to expect.

* Fix typo in test

* Update releasenotes/notes/parameter-float-cast-48f3731fec5e47cd.yaml

Co-authored-by: Kevin Hartman <kevin@hart.mn>

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Co-authored-by: Kevin Hartman <kevin@hart.mn>

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