When Lua is configured without memory restrictions, we use fastpath for table creation (unprotected mode).
In generally it's safe as long as we `abort()` on allocation failure.
However some Lua versions have additional restrictions on table size that we need to adhere in mlua too.
Probably Luau has the lowest limits.
Fixes #627

Instead of locking the VM and making a copy on auxiliary thread, track number of references using Rust ref counter.
This should also help reducing number of used references (they are limited to to 1M usually) on auxiliary thread.

This allow creating a preallocated buffer with specified size initialized to zero.

This can be useful for providing access to buffers through core IO traits.

In particular we cannot yeild across metamethod/C-call boundaries.
This behaviour matches with Lua 5.3+ yielding from hooks only at safe points.
Closes #632

We should not erase thread stack if a bad argument is pushed before resuming the thread.

…ange values between Lua coroutine and Rust.

This functionality is similar to `coroutine.yield` and `coroutine.resume` without C restrictions.