This reverts commit 67c574736912003c377218153f9d3b9c0c96a17b.
[Feature #16275]

and NODE_ZARRAY to NODE_ZLIST.

NODE_ARRAY is used not only by an Array literal, but also the contents
of Hash literals, method call arguments, dynamic string literals, etc.
In addition, the structure of NODE_ARRAY is a linked list, not an array.

This is very confusing, so I believe `NODE_LIST` is a better name.

After 5e86b005c0f2ef30df2f9906c7e2f3abefe286a2, I now think ANYARGS is
dangerous and should be extinct.  This commit deletes ANYARGS from
st_foreach.  I strongly believe that this commit should have had come
with b0af0592fdd9e9d4e4b863fde006d67ccefeac21, which added extra
parameter to st_foreach callbacks.

On ar_table, Do not keep a full-length hash value (FLHV, 8 bytes)
but keep a 1 byte hint from a FLHV (lowest byte of FLHV).
An ar_table only contains at least 8 entries, so hints consumes
8 bytes at most. We can store hints in RHash::ar_hint.

On 32bit CPU, we use 4 entries ar_table.

The advantages:
* We don't need to keep FLHV so ar_table only consumes
  16 bytes (VALUEs of key and value) * 8 entries = 128 bytes.
* We don't need to scan ar_table, but only need to check hints
  in many cases. Especially we don't need to access ar_table
  if there is no match entries (in many cases).
  It will increase memory cache locality.

The disadvantages:
* This technique can increase `#eql?` time because hints can
  conflicts (in theory, it conflicts once in 256 times).
  It can introduce incompatibility if there is a object x where
  x.eql? returns true even if hash values are different.
  I believe we don't need to care such irregular case.
* We need to re-calculate FLHV if we need to switch from ar_table
  to st_table (e.g. exceeds 8 entries).
  It also can introduce incompatibility, on mutating key objects.
  I believe we don't need to care such irregular case too.

Add new debug counters to measure the performance:
* artable_hint_hit - hint is matched and eql?#=>true
* artable_hint_miss - hint is not matched but eql?#=>false
* artable_hint_notfound - lookup counts

Let dump_config boolean members roots and full_heap be bit flags
instead

Closes: https://github.com/ruby/ruby/pull/2274