While doing some code surveys to see what surface/context files are
being used, I discovered that these source files defined classes that
were not used anywhere, so deleting them as dead code.
AKA "Dude Where's My Files?"
Document the history editing that will occur during the monorepo merge.
`flutter/engine` will remain the source of truth of revisions older than
the merge.
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Co-authored-by: Navaron Bracke <brackenavaron@gmail.com>
