[PWA/NavigationCapturing] Implement left-click capturable behavior.

This add tests and logic for capturable behavior. This only supports
the kAuto and kFocusExisting mode right now due to extra capabilities
we need to add for kNavigateExisting.

TODOs are added for follow-up work.

Note: This CL changes some behavior to make it so the aux browsing
context creations do not also enqueue launch params.

Bug: 356233996, 351775835
Fixed: b:359599967
Change-Id: I9bafd1bf111f6e91e3b3e34b10f0a4f0592f530a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5778459
Commit-Queue: Daniel Murphy <dmurph@chromium.org>
Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1341877}