We can use TUPLE2 or TUPLE3 for structs that do not need special
handling by deoptimizer and compiler.

This frees up a few instance types, so that adding the next few
new structs will not cause ABI compatibility to break.

R=mstarzinger@chromium.org

Review-Url: https://codereview.chromium.org/2811183005
Cr-Commit-Position: refs/heads/master@{#44685}