Consider changing outdated Lerna dependency

[rkalis]

We use Lerna for out monorepo setup. We're still on v3, latest is v8.

We've tried updating in the past, but this was hard due to many new major version updates.

Also, I don't think Lerna is the preferred way of doing monorepos any more (I believe you don't even need a separate library these days).

We'll need to properly look into this and either:

• Remove Lerna in favour of new library
• Remove Lerna in favour of native Yarn workspaces
• Update Lerna to v8 (somehow)