The original CL was flaky because deserialization did not wait correctly
for the compilation of missing functions to finish. The baseline-finished
event was set even when there were still some functions missing. The
combination of deserialization and lazy compilation was also not handled
correctly.

Original change's description:
> [wasm] Support partial serialization of modules
>
> At the moment a WebAssembly module can be serialized successfully when
> all functions were compiled with TurboFan. However, for some functions
> it may not be necessary to be compiled with TurboFan, e.g. for functions
> where Liftoff code is as good as TurboFan code.
>
> With this CL we allow WebAssembly modules to get serialized even when
> not all functions are compiled with TurboFan. Missing functions are
> marked as missing in the serlialization. Upon deserialization, missing
> functions either get compiled by Liftoff, or initialized with a
> lazy-compilation stub, depending on the V8 configuration.
>
> Bug: v8:11862

Change-Id: I79a9e8e14199cff87fce6ae41a87087e047bbc65
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3060485Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76017}