Many times in the past, we would ask for an apk based on its package name
and its version code. However multiple repositories provide apks with the
same package name and version code, and such queries would (seemingly)
nondeterministically choose one of these matching apks. This clarifies the
wording in the code around when we explicitly ask for a given apk, and
when we kind of guess which one we want.
Most the time we have an `App` handy, which has a specific repo associated
with it. This allows us to be more specific about requesting `Apk`s.
The times we are kind of guessing is when we rely on the "suggested version
code" of an apk by clicking the misc "Install" or "Upgrade" button in
app details. In the future, we'll need to clear this up so that a more
specific apk is chosen when touching these buttons.
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