- Promote the `Tree` experiment to an example
- Remove sandbox/string.cpp; which is nothing but string_view
- Refactor the Function example so it does not use exceptions
- Remove llist.cpp, which is a mostly uninteresting experiment
- Remove sandbox/array.cpp, which is essentially sprout::array
(see https://github.com/bolero-MURAKAMI/Sprout)
The hidden goal of this commit is also to setup the place for building
without exceptions, by removing or modifying the tests that required
them.
