Port opt_str_uminus to new backend IR

[fresh-eggs]

irb(main):009:0' code = %q{
irb(main):010:0'     def foo()
irb(main):011:0'       -"mosaic"
irb(main):012:0'     end
irb(main):013:0'     foo()
irb(main):014:0> }
=> "\n    def foo()\n      -\"mosaic\"\n    end\n    foo()\n"
irb(main):015:0> puts RubyVM::InstructionSequence.compile(code).disassemble
== disasm: #<ISeq:<compiled>@<compiled>:1 (1,0)-(5,9)> (catch: FALSE)
0000 definemethod                           :foo, foo                 (   2)[Li]
0003 putself                                                          (   5)[Li]
0004 opt_send_without_block                 <calldata!mid:foo, argc:0, FCALL|ARGS_SIMPLE>
0006 leave

== disasm: #<ISeq:foo@<compiled>:2 (2,4)-(4,7)> (catch: FALSE)
0000 opt_str_uminus                         "mosaic", <calldata!mid:-@, argc:0, ARGS_SIMPLE>(   3)[LiCa]
0003 leave                                                            (   4)[Re]

make -j miniruby && RUST_BACKTRACE=1 ruby --disable=gems bootstraptest/runner.rb --ruby="./miniruby -I./lib -I. -I.ext/common --disable-gems --yjit-call-threshold=1 --yjit-verify-ctx" bootstraptest/test_yjit_new_backend.rb

[...]

2022-08-05 12:32:22 -0400
Driver is ruby 3.2.0dev (2022-07-22T22:02:24Z yjit_backend_ir 639815ef68) [x86_64-darwin21]
Target is ruby 3.2.0dev (2022-08-05T16:23:34Z opt_str_uminu abb6670c01) +YJIT [x86_64-darwin21]

test_yjit_new_backend.rb  PASS 79

Finished in 2.63 sec

PASS all 79 tests