The recently added experimental support for non-nullable locals
(https://chromium-review.googlesource.com/c/v8/v8/+/3010283) made
DecodeLocalGet slightly bigger, which caused Clang not to inline
it any more, which has a measurable performance impact because this
is one of the hottest decoding functions. Forcibly inlining it
fixes the regression.

Bug: chromium:1227332
Change-Id: Ifb85f7f5a43ad1c0376bbf37e4af84fb4903371f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3018206Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75676}