tools/metrics: Rewrite DWA codegen tests

Previous tests were not being executed in CI, which caused them to
decay. They were enabled in 7e5c1e82b744232c1ead28a0331180e502959883 and
marked as skipped because they were failing.

This patch rewrites them so that DWA codegen is tested in CI.

Fixed: 448819123
Change-Id: I501f2b8898a4a63a77afa1c0d53c61adba24044e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7030685
Reviewed-by: Jay Zhou <zhouzj@google.com>
Commit-Queue: Kamil Jarosz <kjarosz@google.com>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1530205}