lage version 2.5.2+ broken for lerna and pnpm workspaces.

[curtisman]

Describe the bug
lage version 2.5.2 and above broken for lerna and pnpm workspaces.

lage - Version 2.5.2 - 19 Workers
[09:48:00] - error     Error: <path> is using pnpm which has not been converted to async yet

This is probably a regression from PR #626 which change to use async API from workspace-tools, but those API error out (source) because the async version of the API isn't implemented yet in pnpm.ts and lerna.ts

To Reproduce
Set up a repo using lerna workspace or pnpm workspace and use lage on it.

Expected behavior
It works.

[curtisman]

@kenotron FYI.