OpenQASM 3.0 conversion functions for quantum circuits with enhanced result types.

This namespace provides conversion between quantum circuit data structures
and OpenQASM 3.0 format strings. QASM 3.0 is the latest version of the
OpenQASM quantum assembly language with improved syntax, features, and
comprehensive support for result extraction including measurements,
expectation values, variance, probability, and observables.

Supported QASM 3.0 result extensions:
- Basic measurements (c[i] = measure q[i])
- Observable expectation values (#pragma result expectation)
- Observable variance (#pragma result variance)
- Probability distributions (#pragma result probability)
- Amplitude extraction for specific states (#pragma result amplitude)
- Sample-based measurements with shot specification (#pragma result sample)

Note: State vector and density matrix extraction are simulation-only
and not included in hardware-compatible QASM output.