remove: rpmUtils.TransactionWrapper.returnLeafNodes() method

Unused by dnf, various yum-utils rely on this but the functionality
would be better implemented on repo/sack level which would make it
far more useful than limiting to rpmdb only.
remove: miscutils.pkgTupleFromHeader()

Unused now that returnLeafNodes() is gone from transaction wrapper
remove: miscutils.rangeCompare() and rangeCheck()

Both are entirely unused within dnf
remove: miscutils.formatRequire()

Was imported by cli/output.py but not actually used anywhere within dnf
remove: unused miscutils.rpmOutToStr()
remove: unused string_to_prco_tuple() and imports used only by it
remove: unused miscutils.stringToVersion() and .flagToString()
remove: unused miscutils.compareVerOnly()