swaps the corso go module from github.com/
alcionai/corso to github.com/alcionai/corso/src
to align with the location of the go.mod and
go.sum files inside the repo.
All other changes in the repository update the
package imports to the new module path.
Adds the basic cli-based backup integration test.
Due to discovering some corner cases about panic
conditions and other error handling in bad runtime
state, updates many other packages for safety.
Makes the necessary changes, including adding helper
funcs, to bring the CLI up to an integration-testable
state. The changes made in this commit should be
sufficient for most other CLI tests. Includes a single
test as verification.
