Rename Scala CLI template to example (backport #3917) (#3920)

* Rename Scala CLI template to example (#3917)

This avoids name aliasing with the chisel-template repository.

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Co-authored-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>
(cherry picked from commit bb3c6406

)

# Conflicts:
#	docs/src/installation.md

* Resolve backport conflicts

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Co-authored-by: Jack Koenig <koenig@sifive.com>