Prevent race condition in Attribution Reporting DevTools issue tests

Many of these tests created a promise using dp.Audits.onceIssueAdded()
*after* performing whatever action was expected to result in a DevTools
issue, making the test subject to race conditions:

- disabled-permission-policy-subresource.js
- insecure-attributionsrc-redirect-source.js
- insecure-attributionsrc-redirect-trigger.js
- insecure-context-subresource.js
- insecure-subresource.js
- invalid-source-header.js
- invalid-trigger-header.js

This change reorganizes the tests to always call onceIssueAdded
immediately *before* performing the relevant action.

This change also makes the JS tests use consistent syntax and test
helpers for navigation.

Bug: 1356023
Change-Id: Iea7815c0ae7fe4fa1a7a75aa8cc41186a29f2988
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3854602
Commit-Queue: Andrew Paseltiner <apaseltiner@chromium.org>
Reviewed-by: John Delaney <johnidel@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1039340}