This PR provides lemmas for the tree map functions `get`, `get!` and
`getD` in relation to the other operations for which lemmas already
exist.
Internally, the `simp_to_model` tactic was provided two new simp lemmas
to eliminate some common complications that require `rw`'ing before
using `simp_to_model`. However, it is still necessary to sometimes
`revert` some hypotheses.
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Co-authored-by: Paul Reichert <6992158+datokrat@users.noreply.github.com>
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