Add debug information about which file is loaded from cache
Stop checking conflicts after the first valid package has been found

This avoid looping on each repo for a given package when the chosen one
has already been loaded
Load all version of a given package into universe

Including local and remote even of they both have the same digest
Revert "Load all version of a given package into universe"

This reverts commit 9ccb97dc9e6bf1b80dda7352e4c2726cebe33204.
Revert "Stop checking conflicts after the first valid package has been found"

This reverts commit 6ffd639143876b2a8ce6b34190b4943442ee4a08.
Fix conservative upgrades.