Reland [CUDA][HIP] Fix CTAD for host/device constructors (#168711) (#170481)

Clang currently does not allow using CTAD in CUDA/HIP device functions
since deduction guides are treated as host-only. This patch fixes that
by treating deduction guides as host+device. The rationale is that
deduction guides do not actually generate code in IR, and there is an
existing check for device/host correctness for constructors.

The patch also suppresses duplicate implicit deduction guides from
host/device constructors with identical signatures and constraints to
prevent ambiguity.

For CUDA/HIP, deduction guides are now always implicitly enabled for
both host and device, which matches nvcc's effective behavior. Unlike
nvcc, which silently ignores explicit CUDA/HIP target attributes on
deduction guides, Clang diagnoses device- and host-only attributes as
errors to keep the syntax clean and avoid confusion.

This ensures CTAD works correctly in CUDA/HIP for constructors with
different target attributes and provides clearer diagnostics when users
attempt to annotate deduction guides with CUDA/HIP target attributes.

Example:

```
  #include <tuple>

  __host__ __device__ void func()
  {
    std::tuple<int, int> t = std::tuple(1, 1);
  }
```

This compiles with nvcc but fails with clang for CUDA/HIP without this
fix.

Reference: https://godbolt.org/z/WhT1GrhWE

Fixes: https://github.com/ROCm/ROCm/issues/5646

Fixes: https://github.com/llvm/llvm-project/issues/146646