This commit introduces two new methods on `InstanceAllocator`:
* `validate_module` - this method is used to validate a module after
translation but before compilation. It will be used for the upcoming pooling
allocator to ensure a module being compiled adheres to the limits of the
allocator.
* `adjust_tunables` - this method is used to adjust the `Tunables` given the
JIT compiler. The pooling allocator will use this to force all memories to
be static during compilation.