cuda-core experimental namespace deprecation (attempt v1) - #1377

Update all example files and test Cython files to use cuda.core instead
of cuda.core.experimental:

- Update all example imports from cuda.core.experimental.* to cuda.core.*
- Update example utils imports from cuda.core.experimental.utils to cuda.core.utils
- Update test Cython file imports
- Update build_tests.sh include path from experimental/include to _include

All example files now use the non-experimental import paths.

Update all documentation files to reference cuda.core instead of
cuda.core.experimental:

- api.rst: Change module from cuda.core.experimental to cuda.core
- getting-started.rst: Update currentmodule and example imports
- interoperability.rst: Update currentmodule
- api_private.rst: Update currentmodule
- conf.py: Update system import paths and excluded_dirs paths

All documentation now reflects the new non-experimental API paths.
Release notes files are left unchanged as they are historical.

Update GitHub issue templates and wheel merge script to reference
cuda.core instead of cuda.core.experimental:

- bug_report.yml: Update example references from cuda.core.experimental
  to cuda.core
- feature_request.yml: Update example references from cuda.core.experimental
  to cuda.core
- merge_cuda_core_wheels.py: Update to merge cuda/core/ instead of
  cuda/core/experimental/, and adopt logic that copies only binaries
  into versioned subdirectories while keeping Python modules in cuda/core/

Remove StridedMemoryView and args_viewable_as_strided_memory from
experimental namespace. These should be imported from cuda.core.utils
instead.