When porting an RTOS to the Xtensa architecture, there are a few files that
are common to all Xtensa RTOS ports. These files form the Xtensa RTOS porting
layer (e.g., "xtensa_vectors.S", "xtensa_context.S"). An Xtensa RTOS port is
expected to provide an RTOS specific "xtensa_rtos.h" header to interface with
the Xtensa RTOS porting layer.
Previously, the Xtensa RTOS porting layer files were placed in the FreeRTOS
component. This commit does the following:
1. Moves the Xtensa RTOS porting layer files from the `freertos` component to
the `xtensa` component. The following files were moved:
- xtensa_asm_utils.h
- xtensa_context.S
- xtensa_loadstore_handler.S
- xtensa_vectors.S
2. Refactored xtensa component include paths to separate Xtensa RTOS porting
layer headers.
- Xtensa HAL headers included via `#include <xtensa/...h>`
- Xtensa RTOS porting layer headers included via `#include <...h>`
Note: The xtensa files in the Amazon SMP FreeRTOS port are not moved/deleted in
this commit to ensure the moved files retain a clean diff history.
