These methods are called only during the inlining phase, so even in the
default configuration we follow the same branch as concurrent inlining
and ignore the serialized data. We can thus tighten their return types
and cut down JSBoundFunctionData.

Bug: v8:7790
Change-Id: Ic48f8f2651d684440dc5f6a9934de2ae3a5b5132
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3123410Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76561}