[Bug] [Parser] Let loading QASM files into Graph use ParamParser

[xumingkuan]

Fix #226

This PR fast-forwards the implementation of loading QASM files into Graph to the implementation of loading QASM files into CircuitSeq. There are still a few differences:

1. Loading parameter arrays (OpenQASM 3) is still not supported in Graph.
2. "General controlled gate block" will still be treated as individual gates in Graph, for example, the following is 3 gates in Graph but 1 gate in CircuitSeq.

//ctrl
x q[0];
cx q[0], q[1];
x q[0];

3. Although defining additional qubits after some gates is not allowed in CircuitSeq, it is still allowed in Graph.

This PR also changes the behavior of Graph::to_qasm(). Previously, all parameters were printed in the format pi*0.xxxxxx; now the behavior is:

1. If the compile flag USE_RATIONAL is turned off, when the parameter is a multiple of pi/4, then it will be printed in the format pi*0.xxxxxx; otherwise, it will be printed as a floating-point number directly.
2. If the compile flag USE_RATIONAL is turned on, all parameters are printed in the format pi*a/b, where a and b are integers. Please beware that a can be negative -- there will be cases like pi*-1/4.