Support readout noise in simulators and stim compiler

[João Boechat (joao-boechat)]

Overview

Adds end-to-end support for readout noise (classical bit-flip noise applied
to a measurement result after it is sampled). A measured 0 can be reported
as 1 with probability p_zero_as_one, and a measured 1 as 0 with
probability p_one_as_zero. The feature spans the Stim compiler, the QIR/adaptive
runtime representation, and every simulator back end.

Stim compiler

• Measurement instructions (M/MZ/MX/MY, MR/MRZ/MRX/MRY, and the
  pair measurements MXX/MYY/MZZ) now accept an optional parenthesized
  probability, e.g. M(0.1) 0, and emit a __quantum__rt__readout_noise call
  per produced result. Previously a parenthesized argument was rejected.
• Probability is validated (0 <= p <= 1, at most one argument); a probability
  of 0 emits no noise call.
• Introduced ResultId / QubitId / StimQubitId type aliases to make the
  qubit-vs-result index distinction explicit throughout the QIR writer.

Runtime / QIR representation

• New runtime intrinsic:
  __quantum__rt__readout_noise(double p_zero_as_one, double p_one_as_zero, ptr result).
• New adaptive-bytecode opcode (OP_READOUT_NOISE) and a new
  QirInstruction::ReadoutNoise / QirInstructionId::ReadoutNoise.
• The Python adaptive-profile pass and the aggregate-gates pass lower the
  intrinsic into the new instruction/opcode.

Simulators

Readout noise is supported in all simulators, base profile and adaptive profile:

• CPU full-state simulator
• CPU stabilizer (Clifford) simulator
• GPU full-state simulator