Compilation of wasm functions happens before instantiation. Imports are linked afterwards, at instantiation time. Globals and memory are also
allocated and then tied in via relocation at instantiation time.

This paves the way for implementing Wasm.compile, a prerequisite to
offering the compiled code serialization feature.

Currently, the WasmModule::Compile method just returns a fixed array
containing the code objects. More appropriate modeling of the compiled module to come.

Opportunistically centralized the logic on how to update memory
references, size, and globals, since that logic is the exact same on each
architecture, except for the actual storing of values back in the
instruction stream.

BUG=v8:5072

Review-Url: https://codereview.chromium.org/2056633002
Cr-Commit-Position: refs/heads/master@{#37086}