This moves all asm.js tests (tests that use "%IsAsmWasmCode") into a
separate directory. This will make it easier to skip them all in the
v8_enable_webassembly=false configuration.

R=ahaas@chromium.org

Bug: v8:11238
Change-Id: I805f222b7977f5508f7dbee1f1bd61a88ccd34aa
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2710427
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72900}