update-alternatives.bbclass: Refactor the implementation

update-alternatives.bbclass: Refactor the implementation

Refactor in order to:
  * Deprecate the old interfaces, but keep them for compatibility
  * Provide a new, interface -- capable of working with split packages
  * Each update-alternative will now set proper "per-file" provides

Note: this adds a warning message when the older deprecated behavior is
used.  The older behavior has been fully tested using oe-core.

(From OE-Core rev: 309117d26de6a87b16406a44a0cefcbaaf7b5d7a)

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>