Allow CircuitData construction from PackedOperations and with_capacity(backport #12943 + part of #12809)

[mergify]

Summary

As the title says 🙂 This allows to construct more general circuits than using just CircuitData::from_standard_gates, including e.g. barriers.

Details and comments

This is essentially a copy of CircuitData::from_standard_gates. Qubits and Clbits are now Vec, because

• SmallVec cannot be used as we cannot predict the maximum length
• arrays (&[Qubit]) turned out to be a bit restrictive as the length must be known at compile-time (but maybe there's some trick to use this in the signature but pass vectors or something?)

I didn't yet add a test since it's essentially a copy of the standard gates constructor, and this will be used a bunch by the circuit library refactor. But we could add some cfg test that maybe checks this gives the same circuit data as using the standard gates construct -- though not sure how difficult that comparison is 🙂

Example usage:

let n = 50;  // number of qubits
let h_layer = (0..n).map(|i| (
    StandardGate::HGate.into(),  // PackedOperation
    smallvec![],  //  params
    vec![Qubit(i)],  // qubit
    vec![], // clbit
);
let barrier = (  // barrier on all qubits
    PyInstruction { /* define barrier by calling Python ... */ },
    smallvec![],
    (0..n).map(|i| Qubit(i)).collect(),  // all qubits
    vec![], 
);

let data = CircuitData::from_packed_operations(h_layer.chain(barrier));

---

This is an automatic backport of pull request #12943 done by [Mergify](https://mergify.com).

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[coveralls]

Pull Request Test Coverage Report for Build 10561424816

Details

• 0 of 73 (0.0%) changed or added relevant lines in 1 file are covered.
• 27 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-0.1%) to 89.72%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
crates/circuit/src/circuit_data.rs	0	73	0.0%

Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/expr.rs	1	94.02%
qiskit/transpiler/passes/synthesis/unitary_synthesis.py	2	88.39%
crates/qasm2/src/lex.rs	6	91.73%
crates/qasm2/src/parse.rs	18	96.69%

Totals
Change from base Build 10526731985:	-0.1%
Covered Lines:	66804
Relevant Lines:	74458

---

💛 - Coveralls