This adds the possibility to define non-nullable function tables of heap
types kFunc and user-defined functions. When such table is defined, it
is obligatory to provide an initializer expression after its limits.
Currently, this can only be a function reference.

Changes:
- Change WasmTableObject::raw_type to encode the whole entry type.
- Restructure call_indirect to load the signature only if needed, and
  do null checks only if needed.
- Add the requirement to provide an initializer expression for
  non-nullable tables in module-decoder.
- Rename "global initializer" -> "initializer expression" everywhere.
- Add table initialization in module-instantiate.
- Edit both the C++ and JS WasmModuleBuilder.
- Add and slightly improve tests.
- Format wasm-module-builder.js.

Bug: v8:9495
Change-Id: I7453ee7d567afd5b5fe48a4f1653513787cfe99a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2732673
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73215}