In npm/pnpm/yarn workspace setups, the package manager's list command runs
against the workspace root and may not include packages that are only declared
in a workspace member's package.json.  This caused ng update to report
"Package X is not a dependency" for packages installed in a workspace member
even though they were present and installed.

The fix reads the Angular project root's package.json directly and resolves any
declared dependencies that are resolvable from node_modules but were absent from
the package manager's output.  This restores the behaviour that was present
before the package-manager abstraction was introduced.

Closes angular#32787