Use filer.Filer in bundle/deployer/locker

[pietern]

Summary:

• All remote path arguments for deployer and locker are now relative to root specified at initialization
• The workspace client is now a struct field so it doesn't have to be passed around

[pietern]

@shreyas-goenka The comment diffs are caused by go1.19 formatting doc strings.

I'm following up by making our fmt job use 1.19 so it is consistent with anyone using 1.19 locally.

[pietern]

Manually ran the integration test and it succeeds.

[pietern]

Updated the formatter in #137 and rebased this change on top.

[shreyas-goenka]

LGTM! Question about how well dbfs can work with dabs? Can you keep code assets for execution in dbfs or would have a more limited experience using DAB without files in workspace?

[pietern]

Question about how well dbfs can work with dabs? Can you keep code assets for execution in dbfs or would have a more limited experience using DAB without files in workspace?

It would work fine. You need the workspace for notebooks. Other code can live wherever.

Without files in workspace we need an alternative place to put the deployment state file. It can either be an empty / uninitialized repo, or some path on DBFS, or something else altogether in the future. My intent is to not hardcode to any single approach because none of them will be available to all users.