ZJIT: Specialize polymorphic invokeblock

[k0kubun]

ruby#17653 specializes only one ISEQ per callsite, but we should be able to specialize polymorphic invokeblock.

On lobsters, invokeblock still does a lot of fallbacks:

Top-20 send fallback reasons (99.9% of total 4,747,881):
                             invokeblock_not_specialized: 1,790,399 (37.7%)
                            one_or_more_complex_arg_pass:   916,595 (19.3%)
                          send_without_block_polymorphic:   489,908 (10.3%)
                          send_without_block_megamorphic:   356,682 ( 7.5%)
                                        send_polymorphic:   282,492 ( 5.9%)

and polymorphic seems like the most common reason:

Top-5 invokeblock handler (100.0% of total 1,980,719):
        polymorphic: 1,323,210 (66.8%)
  monomorphic_other:   439,539 (22.2%)
   monomorphic_iseq:   180,526 ( 9.1%)
  monomorphic_ifunc:    34,898 ( 1.8%)
        megamorphic:     2,546 ( 0.1%)

We should probably consider letting the inliner monomorphize such callsites in general, but since it shows up on benchmarks with the inliner enabled, we should consider specializing them as well.