The original intent was to choose packages to which there is most
dependencies. However, since the code has evolved this is has been
mostly obsolete. And in fact now interferes with the provides and
provides priority mechanism. Remove this as obsolete.
Fixes#10742
By introducing a new package metadata field, `provider_priority`
(index letter `k`), we can specify default packages to satisfy a
virtual.
If a user wishes to select an alternative provider for the virtual,
a changeset swapping the default provider for the selected provider
will be generated by the dependency resolver.
Instead of the dependency oriented logic, switch to print them
for each package or name needed. Might give a bit more readable
errors now. There's still few corner cases that proper error is
not output, which are cought by the test cases.
Timo Teräs