This moves the logic for the debug name heuristic, which derives names
for imported and exported entities from the relevant tables, into
wasm-debug.{cc,h} and stores these maps on the DebugInfoImpl rather than
on the WasmModule.

Drive-by-fix: Also use the import table based heuristic for function
names, just like we use it for everything else.

Bug: chromium:1164305
Change-Id: I8a21e0880c680079f63e6607b5b62c788049b9e1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2625870
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Auto-Submit: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72061}