The previous code assumed that trap handling was a global concept, defined
by function trap_handler::UseTrapHandler(). This CL does the first step
in changing the decision to be specifiable at a module level.

Therefore trap_handler::UseTrapHandler() is replaced by
trap_handler::IsTrapHandlerEnabled(), and communicates if compilation
supports the use of trap handlers (but still allowing the use of
bounds checking on memory accesses).

It then refactors the classes ModuleEnv and WasmCompiledModule to have
a field "use_trap_handler" that specifies if traps should be used for
the memory accesses in the module being compiled.

Bug: v8:7143
Change-Id: I9844842d5721c86c2dd55e911b42bf8b9922cf63
Reviewed-on: https://chromium-review.googlesource.com/802322
Commit-Queue: Eric Holk <eholk@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Reviewed-by: Mircea Trofin <mtrofin@chromium.org>
Reviewed-by: Eric Holk <eholk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49915}