Move block coverage logic for TryCatchStatement and TryFinallyStatement
nodes into builder classes.

Bug: v8:6000
Change-Id: I0402ef78a54d6ba1bae62214f16aabfebbd7c581
Reviewed-on: https://chromium-review.googlesource.com/758645
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49268}