* fix: use Chromium's determined new site instance as candidate when navigating.
When navigating to a new address, consider using Chromium's determined site instance
for the new page as it should belong to an existing browsing instance when the
navigation was triggered by window.open().
fixes 8100.
* Revert "fix: use Chromium's determined new site instance as candidate when navigating."
This reverts commit eb95f935654a2c4d4457821297670836c10fdfd5.
* fix: delegate site instance creation back to content when sandboxed.
* fix: ensure site isolation is on
* test: adapt ut for cross-site navigation
* fix: register pending processes during a navigation.
* refactor: dont call loadURL for a window constructed from an existing webContents.
* test: add sandboxed affinity UT's.
* fix: check affinity before deciding if to force a new site instance.
* chore: adapt subsequent patch.
* refactor: constify logically const methods.
* fix: do not reuse site instances when navigation redirects cross-site.
* test: ensure localStorage accessible after x-site redirect.
* test: adapt localStorage acess denied UT for site isolation.
* fix: do not send render-view-deleted for speculative frames.
* chore: amend tests after rebase.
* test: add ut for webContents' render-view-deleted emission
* fix: introduce current-render-view-deleted for current RVH's deletions.
Revert render-view-deleted to being emitted with any RVH's deletion.
current-render-view-deleted is emitted only when the RVH being deleted
is the current one.
* refactor: style and comments fixed.
