Adds a new CMake option to disable the usage of incomplete headers.
These incomplete headers are not guaranteed to be ABI stable. This
option is intended to be used by vendors so they can avoid their users
from code that's not ready for production usage.
The option is enabled by default.
Differential Revision: https://reviews.llvm.org/D106763
* adds `sized_range` and conformance tests
* moves `disable_sized_range` into namespace `std::ranges`
* removes explicit type parameter
Implements part of P0896 'The One Ranges Proposal'.
Differential Revision: https://reviews.llvm.org/D102434
zoecarver