gas/ELF: widen use of $dump_opts in testsuite

gas/ELF: widen use of $dump_opts in testsuite

Rather than special-casing rx-*-* for section30, force use of
conventional section names uniformly. By further passing $dump_opts to
a few more tests, a number of xfail-s (and one notarget) can be
eliminated (some of which had wrong justifications in associated
comments anyway). Note that section7 and section15 need to be left
alone: The harness fiddling with section names there didn't help before
and is getting in the way now. For section12b, section16b, and most of
the Dwarf tests nothing changes. Interestingly by passing $dump_opts
the need to xfail section11 for LoongArch and RISC-V also goes away.