oe-pkgdata-util: improve lookup-pkg error for RPROVIDES packages

oe-pkgdata-util: improve lookup-pkg error for RPROVIDES packages

When a package is not found by 'oe-pkgdata-util lookup-pkg', the error
message provides no guidance on what went wrong or where to look.

Improve the error message by checking the runtime-rprovides directory
for the missing package. If the package exists in RPROVIDES:

 - If the provider package was generated, suggest looking up the actual
   package name instead.
 - If the provider package was not generated (e.g. empty package or
   disabled by PACKAGECONFIG), inform the user which recipe provides it
   and that it was not generated.

This helps users quickly identify the correct package name or
understand why a package is missing from their build.

Before:
  ERROR: The following packages could not be found: eglibc

After:
  ERROR: eglibc is in the RPROVIDES of glibc (recipe: glibc), try
  looking up 'glibc' instead

[YOCTO #16083]

Signed-off-by: Zk47T <zizuzacker@gmail.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>