Ruby

Skip ObjectSpaceTest#test_count_nodes for RBS

Remove ObjectSpace.count_nodes

ObjectSpace.count_nodes has been a no-op and returning an empty hash since
Ruby 2.5 because parser nodes are not GC managed.

[DOC] Doc for Enumerator.new

[DOC] Doc for Enumerator class

[DOC] Harmonize #> methods

YJIT: Add frozen guard for struct aset (#15835)

We used to just skip this check (oops), but we should not allow
modifying frozen objects.

YJIT: gen_struct_aset check for frozen status

Optimize rb_mark_generic_ivar for T_DATA and T_STRUCT

T_DATA and T_STRUCT could have ivars but might not use the generic_fields_tbl.
This commit skips lookup in the generic_fields_tbl for those cases.

Rename alloca_overflow to stack_overflow

alloca is an implementation detail to raise a stack overflow.

Use assert_ruby_status if no assertion