fixup to free_and_set_cop_warnings()

fixup to free_and_set_cop_warnings()

v5.31.9-156-g94c8b9c1f0 introduced the free_and_set_cop_warnings()
macro. It's first argument expects a COP rather than a COP*. Its usage
in S_restore_cop_warnings(() is to modify PL_cucop, but in order to pass
a COP rather than a COP*, the original commit made a local copy of
PL_curcop and ended up inadvertently updating the copy instead.

This commit changes the maco so it expects a COP*, and updates the bulk
of its callers to use &PL_compiling rather than PL_compiling, and fixes
up S_restore_cop_warnings().

The symptoms were ASAN failures in a few test scripts including
uni/parser.t and ext/XS-APItest/t/handy0*.t.

(The S_restore_cop_warnings() function was only used by
Perl__force_out_malformed_utf8_message(), so didn't cause many issues
outside of test scripts which forced such "malformed "errors).