introduce autotools deprecation warning
Description
As autotools will be deprecated in the future, we are now printing a warning (with user confirmation) at the end of the configure script.
This warning can be disabled with the --enable-silent_deprecation
flag.
News snippet
Deprecate autotools.
Checklist
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I have checked that my code follows the Octopus coding standards -
I have added tests for all the new features added in this request.