🐛 Custom Gate Definitions don't follow OpenQASM standard

Environment information

Any environment

Description

Two aspects of the OpenQASM standard are not respected by the current implementation for custom gates:

• Custom gate definitions cannot access underlying registers, only the qubits that were passed to them. The current implementation assumes this is possible, so dome of the parsing and data dependency logic is incorrect, and assertions can access quantum registers even in custom gate definitions.
• Custom gate definitions should also support angle parameters, which, at the moment, they don't.

Expected behavior

Something like this should not work:

qreg q[3];
gate test t {
    assert-ent t, q[0];
}

Something like this should work:

gate test(x) t {
    ...
}

How to Reproduce

Run the two code snippets above in the debugger.

Start by running the two OpenQASM snippets in the debugger and tracing the custom-gate parsing and data-dependency logic mentioned in the report. Done means register access from inside a custom gate is rejected while angle parameters in custom gate definitions are accepted.