src: lazily initialize global BuiltinLoader
Using simdutf during startup can fail when compilation units are linked in the wrong order by a static initialization order issue.
https://github.com/nodejs/node/pull/45942 would also solve this, but since that is a larger effort, this patch focuses on solving the immediate problem. Alternatively, simdutf should arguably be made usable during static initialization, but that is also not as straightforward as this patch.