lib/string_helpers: Introduce managed variant of kasprintf_strarray()

lib/string_helpers: Introduce managed variant of kasprintf_strarray()

Some of the users want to have easy way to allocate array of strings
that will be automatically cleaned when associated device is gone.

Introduce managed variant of kasprintf_strarray() for such use cases.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>