Revert "Start migration of try/throw/catch to match proposal."

This reverts commit 470a1001.

Reason for revert: Speculative:
https://build.chromium.org/p/client.v8/builders/V8%20Mac%20GC%20Stress/builds/14520
Also flaked later:
https://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20gc%20stress/builds/11953

Original change's description:
> Start migration of try/throw/catch to match proposal.
> 
> This CL does the first baby steps on moving the current (experimental)
> exception handling to match that of the WebAssembly proposal.
> 
> It does the following:
> 
> 1) Use exception tags instead of integers.
> 
> 2) Only handle empty exception signatures (i.e. no values associated
>    with the exception tag.
> 
> 3) Only handle one catch clause.
> 
> 4) Be sure to rethrow the exception if the exception tag does not match.
> 
> Note: There are many things that need to be fixed, and are too
> numerous to list here. However, the code should have TODO's on each
> missing parts of the implementation.
> 
> Also note that the code currently doesn't handle nested catch blocks,
> nor does it change the throw value being an integer. Rather, the
> integer value is still being thrown, and currently is the exception
> tag. Therefore, we don't build an exception object. This is the reason
> why this CL doesn't handle exceptions that pass values.
> 
> Also, the current implementation still can't handle multiple modules
> because tag resolution (between) modules has not be implemented yet.
> 
> Bug: v8:6577
> Change-Id: Id6d08b641b3c42d1eec7d4db582f2dab35406114
> Reviewed-on: https://chromium-review.googlesource.com/591910
> Reviewed-by: Brad Nelson <bradnelson@chromium.org>
> Commit-Queue: Karl Schimpf <kschimpf@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#47087}

TBR=bradnelson@chromium.org,eholk@chromium.org,kschimpf@chromium.org

Change-Id: I91709105fb066c08b43766b0bc76db8a3af5c9d9
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:6577
Reviewed-on: https://chromium-review.googlesource.com/598947Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47093}