`migrate-db`: automate more steps of bbolt to SQL migration process

Right now there are a number of steps that need to be manually run **before** `lndinit migrate-db` can be run. These are mentioned at

https://github.com/lightninglabs/lndinit/blob/fb30cf3887a925755eb3118ff653f6a5bc6d9bf0/docs/data-migration.md?plain=1#L56-L89

I believe that we should make `lndinit migrate-db` smart enough to handle all of these steps for us automatically (inside of `lndinit`) without having to manually start LND extra times. Also, if they have been complete already, `lndinit migrate-db` should be smart enough to quietly move on and not error out.

We may also want to allow some flags to be passed to `lndinit migrate-db` to force the skipping of any of those steps (especially the optional ones) if we want, but we should default to them all being attempted.

Read docs/data-migration.md, especially lines 56-89, and trace the lndinit migrate-db entry point. Map each manually required migration step into the command, including behavior when a step was already completed and any optional-step skip flags. Done means the documented pre-migration steps are attempted automatically without extra LND starts and completed steps do not cause errors.

Written by the indexing model from the issue text.