Cancelling a kit pull with ctrl+c leaves partially downloaded layers in storage

[amisevsk]

Describe the bug
Kit saves partially-downloaded layers to an ingest directory, and moves them into actual storage when the upload is completed. However, it does not clean these files up if the download is killed unexpectedly (e.g. via ctrl-C), leaving those files to consume storage space.

To Reproduce

1. Begin downloading a modelkit with at least one larger layer
2. Cancel the download partway through via ctrl+C
3. Look in <kitops-home>/storage/<repo>/ingest to see partially downloaded tmp files.

It's not clear when these files are cleaned up, and in my testing, even a kit remove -a -f will not remove them.

Version
nightly

Additional context
Related to #311 -- these files could be used to resume downloads.