Add back fallback wasm-trap handling

Crashpad was understood to be unconditionally enabled in
https://crrev.com/c/5237441. Turns out that that wasn't true for
content_shell.

This change sets up wasm-trap handling for the case where content_shell
has not enabled crash reporting but moves the responsibility to
ShellContentRendererClient. The default ContentRendererClient assumes
that crash reporting is enabled (crashpad enabled by default) and does
not set up its own handler.

Bug: 327517309
Change-Id: If3d5f9a313c22e5926d276e6fdfbe9fefe20445d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5372409


Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Commit-Queue: Peter Boström <pbos@chromium.org>
Reviewed-by: Charlie Reis <creis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1277046}