[clang] StmtPrinter: Handle DeclRefExpr to a Decomposition (#125001)
A DeclRefExpr could never refer to a Decomposition in valid C++ code,
but somehow the Analyzer creates these entities and then it tries to
print them.
There is no sensible answer here, so we print 'decomposition' followed
by the names of all of its bindings, separated by dashes.