CLI: Be monorepo aware

[josephjclark]

Now that we have a monorepo, we should make devtools aware of it.

If you're developing a language adaptor, you'll be writing it in the monorepo. You want to be able to use the new CLI to test that adaptor against jobs.

If you give the CLI a path to the monorepo, any adaptor imports should load straight from the monorepo.

This can be used a couple of ways:

• pass in a monorepo=path/to/monorepo flag (or -m path/to/monotro)
• Set an env var and pass a -M flag to the CLI (makes monorepo use easy but still won't load from the monorepo by default)

Some thoughts:

• We should load from the build, not the source (this also ensures that .d.ts files are there)
• Logging should make it very clear when adaptors have been loaded out of the monorepo (success level logging)
• If using the monorepo all version stuff is ignored - no autoinstalls or anything, and any version directives in job code will be ignored