cleanup: include/: move flash_map.h to storage/flash_map.h

move flash_map.h to storage/flash_map.h and
create a shim for backward-compatibility.

No functional changes to the headers.
A warning in the shim can be controlled with CONFIG_COMPAT_INCLUDES.

Related to #16539

Signed-off-by: Anas Nashif <anas.nashif@intel.com>
17 files changed