[packages] Make repo tooling workspace-friendly #190453

#161385 covers actively using workspaces in the repo tooling, but as a much smaller set of work, we should make the repo tooling not actively interfere with workspaces; currently, it mostly has not been tested with it, so there are unknown sharp edges.

One known issue we've encountered is that when material_ui tried to enable workspaces for the library and its example, the next change to cupertino_ui failed pathified analysis with:

Running command: "flutter pub get" in /b/s/w/ir/x/w/packages/packages/material_ui
The package `cupertino_ui` is overridden in both:
package `material_ui` at `.` and 'material_ui_examples' at `./example`.

Consider removing one of the overrides.
Failed to update packages.

So at least make-deps-path-based will need logic updates to behave differently when modifying packages that use workspaces.