This deprecates the following result variables:
* ARMADILLO_VERSION_STRING
* ARMADILLO_VERSION_MAJOR
* ARMADILLO_VERSION_MINOR
* ARMADILLO_VERSION_PATCH
* ARMADILLO_VERSION_NAME (added the Armadillo_VERSION_NAME as an
alternative).
When Armadillo is found in config mode, the `Armadillo_VERSION` is
already set automatically:
find_package(Armadillo CONFIG)
Issue: #27088