Unchecked memory consumption with `memory.atomic.wait{32,64}`

[alexcrichton]

This program:

      (module
        (memory (export "mem") 65536 65536 shared)
        (func (export "run") (param $end i32)
          (local $i i32)
          (block $done
            (loop $l
              (br_if $done (i32.ge_u (local.get $i) (local.get $end)))
              (drop (memory.atomic.wait32 (local.get $i) (i32.const 0) (i64.const 0)))
              (local.set $i (i32.add (local.get $i) (i32.const 4)))
              (br $l)
            )
          )
        )
      )

when invoked as:

$ wasmtime -Wshared-memory --invoke run foo.wat 1000000000

will consume an unbounded amount of memory allocating wait queues on addresses which are never cleaned up (within Wasmtime's ParkingSpot implementation)