Refactor vm->mark_object_ary to be a linked list of WB protected objects

[casperisfine]

Fix: #10171

This st_table is used to both mark and pin classes defined from the C API. But vm->mark_object_ary already does both much more efficiently.

Currently a Ruby process starts with 252 rooted classes, which uses 7224B in an st_table or 2016B in an RArray.

So a baseline of 5kB saved, but since mark_object_ary is preallocated with 1024 slots but only use 405 of them, it's a net 7kB save.

vm->mark_object_ary is also being refactored.

Prior to this changes, mark_object_ary was a regular RArray, but since this allows for references to be moved, it was marked a second time from rb_vm_mark() to pin these objects.

This has the detrimental effect of marking these references on every minors even though it's a mostly append only list.

But using a custom TypedData we can save from having to mark all the references on minor GC runs.

Addtionally, immediate values are now ignored and not appended to vm->mark_object_ary as it's just wasted space.

cc @peterzhu2118

[casperisfine]

So a baseline of 5kB saved, but since mark_object_ary is preallocated with 1024 slots but only use 405 of them, it's a net 7kB save.

I checked the number on a large application.defined_module_hash has 1k entires for a memsize of 28728B, and mark_object_ary 3242 entries. So there the saving is rougthly 20KB, and saves marking 4.2k objects on every minors.