Add IPO support for Visual Studio (which is referred to by VS as
"Link Time Code Generation" and "Whole Program Optimization"), for
VS version >= 10. This allows CMake/VS users to enable IPO by setting
property `INTERPROCEDURAL_OPTIMIZATION`.
Fixes: #16748
Previously the `INTERPROCEDURAL_OPTIMIZATION` target property was
honored only for the Intel compiler on Linux and otherwise ignored. In
order to add support for more compilers incrementally without changing
behavior in the future, add a new policy whose NEW behavior enforces the
`INTERPROCEDURAL_OPTIMIZATION` property. Add flags for supported
compilers and otherwise produce an error.
