Remove deprecated code and interfaces

This removes the following deprecated code:

• Remove support for passing functions providing only f.evaluate(x,y) to interpolate() and corresponding checks. This was deprecated in 2.8.
• The utility Impl::makeFunctionWillCallOperator() was only needed to provide interpolate() support for f.evaluate(x,y) and y = f(x) at the same time. The deprecated overload for the former has been removed. The do-nothing overload for the latter has been deprecated. As part of Impl:: it could be removed right away, but this was also used in downstream modules.
• Remove deprecated class LocalFiniteElementFunctionBase which was once needed for the old interpolate() interface.
• Remove deprecated headers and classes from lagrange/.
• Undeprecate accidentally deprecated headers in lagrange/
• Remove the overloads numLagrangePoints(topologyId,...) and equidistantLagrangePoints(topologyId,...) based on topology ids. Both have been deprecated 2.8.
• Remove deprecated workarounds for clang < 6.