Support datatype destructors in the Rust backend (dafny-lang#4353)

Support datatype destructors in the Rust backend




<small>By submitting this pull request, I confirm that my contribution
is made under the terms of the [MIT
license](https://github.com/dafny-lang/dafny/blob/master/LICENSE.txt).</small>

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* dafny-lang#4369
* dafny-lang#4368
* dafny-lang#4363
* dafny-lang#4361
* __->__ dafny-lang#4353