Handle fact that Lerna is no longer maintained

I see that this module relies on four Lerna modules:

https://github.com/googleapis/release-please/blob/f5484e90024363c06e36ca89fab2b2ca5cf1455d/package.json#L62-L65

Used in the `node-workspace.ts`:

https://github.com/googleapis/release-please/blob/9659c1c868395394a40ff8f6caf9aaa7998fb8b8/src/plugins/node-workspace.ts#L15-L16

There is an ongoing discussion in the Lerna project on the fact that it is no longer maintained, and how to move forward: https://github.com/lerna/lerna/issues/2703

I thought I would open an issue / question here to notify you + gather your point of view on this and whether you think a move to `yarn` or `npm` workspaces would be a good way forward for `release-please` or whether eg. a fork of the `version` and `publish` commands of Lerna (as suggested in https://github.com/lerna/lerna/issues/2703#issuecomment-1017701131) would be preferable.