LoadGlobalIC will be inlined into ignition's LdaGlobal family of bytecode
handlers.  This CL splits up LoadGlobalIC into three distinct cases (property
cell, handler, and miss) and introduces the ExitPoint abstraction in order
to make inlining easier.

BUG=v8:5917

Review-Url: https://codereview.chromium.org/2688503002
Cr-Commit-Position: refs/heads/master@{#43055}