Make the AsmWasmBuilder drive the process of typing and potentially parsing
function bodies. This will allow us to keep only a single asm.js function's
AST in memory as we convert to WebAssembly.
This is needed to keep our memory footprint low.

Add some additional output to a few tests that's helpful to see which stage they fail at.

BUG= https://bugs.chromium.org/p/v8/issues/detail?id=4203
LOG=N
R=marja@chromium.org,adamk@chromium.org,aseemgarg@chromium.org,titzer@chromium.org

Review-Url: https://codereview.chromium.org/2398023002
Cr-Commit-Position: refs/heads/master@{#41372}