Missing or incorrect source location in the SCFG output

[sklam]

SCFG should retain source location of the original AST.

It's currently set to line 0 for many new nodes: e.g https://github.com/numba/numba-rvsdg/blob/77a957a232f70d1868cdcaec10adb324571b5c1c/numba_rvsdg/core/datastructures/ast_transforms.py#L690