Support for symbolic expressions in FreeParameters

[kshyatt-aws]

Describe the feature you'd like Currently only numerical values are allowed for FreeParameter. We should replicate the Python BDK support for FreeParameterExpression, allowing gates like Rx( 2 * alpha /3), for example.

Is this feature already present in the Python SDK? Yes. https://github.com/amazon-braket/amazon-braket-sdk-python/blob/main/src/braket/parametric/free_parameter_expression.py

How would this feature be used? Please describe. This would allow more complex expressions for parametrized gates.

Describe alternatives you've considered Currently users have to create new parameters to capture cases like 2 * alpha.

Additional context An appropriate Julia package should be chosen for the symbolic expressions. SymbolicExpressions.jl is one example.