This extends the test coverage for source position tracking of ToNumber
conversion to also test conversion to "double" type. It also fixes the
discovered inconsistencies. Note that the conversion to "float" remains
untested as imported functions are not allowed have "float" return type.

R=clemensh@chromium.org
TEST=mjsunit/wasm/asm-wasm-exception-in-tonumber
BUG=v8:6127

Change-Id: I6c59b7a24456a585a814f19a86eb9447ac5098ab
Reviewed-on: https://chromium-review.googlesource.com/467251
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44409}