[devtools] Import test runners in http/tests/devtools/search

This CL replaces 'TestRunner.loadTestModule' calls with import
statements.

The CL was fully auto-generated by a small regex search&replace script.

R=kprokopenko@chromium.org

Bug: 1442410
Change-Id: I12b07769cd4a45ec916a259b3b9df3055a6b422d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4548923


Reviewed-by: Kateryna Prokopenko <kprokopenko@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1147661}