Promote "history sharing on invite" out of developer options (#6647)
* Enable history sharing by default, unconditionally
* Remove feature-flag dep from history viz icons in room header
* Remove feature-flag dep from warning on inviting new people
* Remove feature-flag dep from warning on starting chat with new people
* Remove `enableKeyShareOnInvite` feature flag
* Update screenshots
* Remove redundant `FakeFeatureFlagService()` invocation, per review comment
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Co-authored-by: ElementBot <android@element.io>