BasH5Reader 2x speedup in common use case: index the region table at file load time

[Tracking bug 22690]

[git-p4: depot-paths = "//depot/software/bioinformatics/lib/python/pbcore/": change = 122502]
Another big speedup for Zmw::hqRegion

[Tracking bug 22690]

[git-p4: depot-paths = "//depot/software/bioinformatics/lib/python/pbcore/": change = 122503]