This CL includes several small bug fixes for trap handlers. Among the changes:

* Use the correct representation for ProtectedLoads, enabling protected loads of
  floating point types.

* Including the protected instruction list in what gets serialized for Code
  objects. This is needed to allow deserialization for Wasm modules to work.

* Get the context needed to through and exception from the Isolate rather than
  getting it as a parameter to the Protected instructions. Passing it in as an
  argument is problematic when code is compiled ahead of time, as the context
  may not be known yet. The new approach is similar to how it works for TrapIf
  and TrapUnless.

BUG= https://bugs.chromium.org/p/v8/issues/detail?id=5277

Review-Url: https://codereview.chromium.org/2591903002
Cr-Commit-Position: refs/heads/master@{#41907}