Implementation of classical expressions: RFC 10 #10239
Description
What should we add?
This is the tracking epic for RFC 10: preliminary representation of classical expressions. Details of the proposal are in the linked document.
### Required
- [ ] https://github.com/Qiskit/qiskit-terra/issues/10223
- [ ] https://github.com/Qiskit/qiskit-terra/issues/10224
- [ ] https://github.com/Qiskit/qiskit-terra/issues/10233
- [ ] https://github.com/Qiskit/qiskit-terra/issues/10289
- [ ] https://github.com/Qiskit/qiskit-terra/issues/10225
- [ ] https://github.com/Qiskit/qiskit-terra/issues/10234
- [ ] https://github.com/Qiskit/qiskit-terra/issues/10331
### Strongly desired for 0.25
0. [ ] https://github.com/Qiskit/qiskit-terra/issues/10228
### Long term required, not necessary for 0.25
0. [ ] https://github.com/Qiskit/qiskit-terra/issues/10232
0. [ ] https://github.com/Qiskit/qiskit-terra/issues/10236
0. [ ] https://github.com/Qiskit/qiskit-terra/issues/10238