fix: avoid unittest link oom

[tychoish]

This is partially speculative, but the general plan is:

• move the integration tests out of the cli crate because they're
  orthogonal (they depend on the binary existing, which is already
  taken care of), and (would seem likely to) create a lot of linking
  workload.

• disable doctests in places where they aren't needed (this mostly
  just reduces noise in the test output that I found confusing)

• collapse legacy makefile testing. (I think passing workspace
  invalidates some cache for local builds, so this will probably make
  things easier in the long run.)

• disable test builds for all packages that don't actually have
  tests. We'll still have to compile them as dependencies, but
  hopefully that's easier.

In the future we should rename the CI task, but that's fussy and
breaks PR for fussiness. Can try to remember to change later.