[EPIC] Track breaking changes for CCCL 3.0

[jrhemstad]

This issue is to keep track of breaking changes we'd like to make in the next major version release.

Removals

• Drop CI runs for CTK 11.x #3249
• Drop CTK 11.1 support in code #3284
• Require C++17 for compiling Thrust and CUB #3252
• Require C++17 for compiling libcu++ (pending confirmation from relevant users)
• Remove CDPv1 Support
• Drop all deprecated CUB APIs accepting a debug_synchronous parameter
• Drop deprecated ::result_type etc. from Thrust function objects (and alias them to the libcu++ ones) #3271
• Remove all code paths and policies for SM35
• Drop CUB iterators existing in Thrust
• Remove clang <14 from CI #3184
• Drop support for VS 2017 in code
• Drop Thrust's deprecated compiler macros #3301
• Drop CUB's util_compiler.cuh #3302
• Drop CUB_RUNTIME_ENABLED and __THRUST_HAS_CUDART__ #3305
• Drop Thrust's compiler_fence.h #3300
• Drop Thrust legacy arch macros #3298
• Drop support for Intel ICC in code #3278
• Drop VS 2017 from CI #3286
• Drop CUB legacy macros in util_arch.cuh #3256
• Drop cub::Mutex #3250
• Drop Intel ICC from CI #3276
• Drop thrust::[unary|binary]_function #3273
• Drop thrust unary_traits and binary_traits #3259
• Drop thrust not1 and not2 #3263
• Drop support for GCC6 #3267

Deprecations (No scheduled removal yet)

• Deprecate thrust::optional #3306
• Move CUB agents to internal namespace #3303
• Deprecate CUB iterators which exist in Thrust or libcu++ #3261
• Deprecate Thrust's cpp_compatibility.h macros #3299
• Deprecate thrust::async #100
• Deprecate and replace cub::min/max by cuda::std::min/max
• Consider dropping cub::DeviceSpmv in favor of cuSPARSE #3070
• Review and deprecate features from CUB util_ptx.cuh #3289
• Replace use of thrust::identity by cuda::std::identity #2762
• [FEA]: Deprecate GridBarrier and GridBarrierLifetime #1389

We should backport those to the 2.8 branch.

API breaking changes

• [BUG]: thrust::transform_iterator<F, ...> is broken if F is not copy_assignable #2393
• Make thrust::identity::operator() have the same return type as cuda::std::identity::operator()
• [FEA]: ceil_div should return the resulting type of its operation #2845
• Swap order of template parameters of DispatchBatchMemcpy and DispatchReduce so policy hub is last
• Replace boolean parameters of CUB dispatchers by enumerations (@elstehle)
• Assert offset type in DispatchScan to be unsigned
• Move all CUB dispatchers into internal namespaces #3094
• Extended floating-point type replacement (TODO: needs more explanation)
• Thrust universal_host_pinned_memory_resource's pointer type should probably be a universial_ptr #2659

ABI breaking changes

• Deprecate and drop old libcu++ ABI namespaces

Behavioral changes

• Unify accumulator type handling across CUB/Thrust
• Unify initial value handling across CUB/Thrust
• Remove multiplication and division nan handling <complex> Enable users to disable normalization for division too. libcudacxx#474 (review)
• Remove ::result_type detection from Thrust result_of_adaptable_function

Cleanup

• [FEA]: Refactor user-facing Thrust types to use libcu++  #34
• Replace our current mdspan implementation with one derived from the newer llvm implementation
• Review and deprecate macros from thrust/thrust/system/cuda/config.h