[libsycl] Generic code cleanup (#224330)
- aligns SYCL API parameter names with specification
- fixes doxygen keywords used in comments
- applies CamelCase to all non-SYCL 2020 vars and methods
- applies generic recomendations from LLVM coding standards
- fixes missing or redundant headers
- adds detail namespace to the helpers if missed
- a few tests were renamed to match their content
Assisted-by: Claude Code.
---------
Signed-off-by: Tikhomirova, Kseniya <kseniya.tikhomirova@intel.com>
