[test] Use Template::Set with const char* name in test-api.cc

Bug: v8:10884
Change-Id: I961033da39fea6e2e165aabb978208b581cfeaf0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2412170Reviewed-by: Dan Elphick <delphick@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69916}