Since enabling of GC64 Lua memory can go very high, leading to unexpected OOM across the whole server, instead of just pure OutOfMemory exception inside single instance. So, we need to implement explisit option to cap the memory with ability to change it.

Proposal: new option in section lua:

lua:
    memory: 2147483648

Default value should be set to 2Gb (2147483648)

Like memtx.memory it could not be lowered, but it whould be good to have an ability to raise it dynamically.