A node in the control-flow graph of CoverageGraph.
BasicCoverageBlockData holds the data indexed by a BasicCoverageBlock.
A coverage-specific simplification of the MIR control flow graph (CFG). The CoverageGraphs
nodes are BasicCoverageBlocks, which encompass one or more MIR BasicBlocks.
Maintains separate worklists for each loop in the BasicCoverageBlock CFG, plus one for the
CoverageGraph outside all loops. This supports traversing the BCB CFG in a way that
ensures a loop is completely traversed before processing Blocks after the end of the loop.