Revert "[amberctl] Mirror source edits to pkg_resolver"

This reverts commit 96f91478.

Reason for revert: Breaks tests of SDK consumers.

Original change's description:
> [amberctl] Mirror source edits to pkg_resolver
> 
> To ease the migration from using amber source configs to using
> pkg_resolver repository configs, this change modifies the source
> management commands in amberctl to perform roughly equivalent operations
> on the RepositoryManager and rewrite.Engine.
> 
> Test: modified amberctl test to verify pkg_resolver state
> 
> PKG-704 #done
> 
> Change-Id: I92853a61b59a60693014853862a9494c9d227caa

TBR=raggi@google.com,etryzelaar@google.com,kevinwells@google.com,computerdruid@google.com,galbanum@google.com

Change-Id: Ie0621d15882b5f71bc737fa2a9558b6d965cc361
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