Fix QPY support for control flow instructions

This commit fixes support for using qpy serialization with circuits that
contained control flow instructions. Previously, if you attempted to
serialize a circuit that contained control flow instructions it would
error as qpy didn't support embedding the circuit blocks as parameters
for the instructions. This has been fixed and other missing pieces for
fully reconstructing circuits with control flow were added. This
requires bumping the version string to v4 because to accurately
reconstruct control flow circuits we needed to be able to represent
registers that were only partially present in a circuit fully. V4 also
adds a representation for ranges which didn't exist in earlier versions.

Fixes Qiskit#7583