* Turn on revive linter, ignore only a few things
* Fix lint errors
Ignore shadowing of 'suite' in tests for now. Also move some constants
that had the same value to tester.
The alias of testing to ctesting prevented auto-importing
of the testing library. This change (arbitrarily) renames
the package so that it doesn't collide with the core pkg
for "testing".
* Split KopiaWrapper into repo handle and logic
With ModelStore, multiple structs need a reference to the kopia repo.
Make a small wrapper class (conn) that can open and initialize a repo. The
wrapper handles concurrent closes and opens and does ref counting to
ensure it only drops the kopia handle when the last reference is closed.
Rename KopiaWrapper to Wrapper and keep backup/restore functionality
in it.
