package_manager/rpm: give out useful reason about unmatched packages

package_manager/rpm: give out useful reason about unmatched packages

Unmatched package error is a common error at rootfs. We want to give
out more useful information to user.

Before this change, if some user specifiy IMAGE_INSTALL += "catch2",
the error message will be like:

  No match for argument: catch2
  Error: Unable to find a match: catch2

With this patch, the error message will be like:

  No match for argument: catch2
  Error: Unable to find a match: catch2
  catch2 is a recipe. Its generated packages are: ['catch2-src', 'catch2-dbg', 'catch2-staticdev', 'catch2-dev', 'catch2-doc']
  Either specify a generated package or set ALLOW_EMPTY:${PN} = "1" in catch2 recipe

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>