storage/stream_flash: Deprecate stream_flash_erase_page

The commit marks stream_flash_erase_page as deprecated.
After the function is removed users will have to rely on stream
flash to erase space it needs prior to write.

The stream_flash_erase_page has several issues like using non-relative
offset for erases, allowing to destroy data already written or even
erase out of area available for stream flash.

This fixes #67407

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>