Both js-to-wasm-wrapper-cache-inl.h and wasm-import-wrapper-cache-inl.h
do not include any inl headers, thus they can be plain headers. If they
ever need to include inl headers again, we should split out the
respective functions into a separete inl header to follow the usual
pattern to have *both* a plain header *and* an inl header.

R=mstarzinger@chromium.org

Bug: v8:8834
Change-Id: I1b1b917a8e2c47f1354522479f8c57475bee6244
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1535826Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60431}