When we store the typed text for a browser, we should probably also store search mode.

Use-cases:
a) I start searching in a tab, move to a different window/tab to copy something, go back and expect to still be in search mode with the appropriate engine
b) I restart the browser with a typed search, it should go restore that browser in search mode with my typed search

This seems like it could be a dupe of bug 1647899? Although the scope of this bug is wider.

let's transform this to track windows and sessions only, just in case.

Pointing out bug 1647899 comment 6 over here, since it could form a good basis for this work.

I think a) now works as expected, so the only remaining thing here is Session Restore.

in https://bugzilla.mozilla.org/show_bug.cgi?id=1647899#c7 Drew suggested to keep storing info in the urlbar, so potentially we can just have session store interact with the urlbar modules to apply and retrieve the state.

This is a WIP that basically works, but it needs more tests and some rough edges
smoothed out.

https://treeherder.mozilla.org/#/jobs?repo=try&revision=60ed50b6d07b8bd8411205e9fa6a4150015e90a7

https://treeherder.mozilla.org/#/jobs?repo=try&revision=72e2db0b7967cd2436243eb5abe31179b303d9f0

https://treeherder.mozilla.org/#/jobs?repo=try&revision=eb92fca37d141f39a4ea2404ee09caf278bde5ee

https://treeherder.mozilla.org/#/jobs?repo=try&revision=ab70388b329eecb098443b6522545e3391788635

https://treeherder.mozilla.org/#/jobs?repo=try&revision=4a39a8ee08703c1c474f625a96d248b9350b0216

https://hg.mozilla.org/mozilla-central/rev/9b3560927e84