Kiln/0.79.0 requires a Kilnfile

[abg]

Describe the bug

$ kiln version
kiln version 0.79.0
$ kiln bake ...
2023/04/04 10:16:30 could not execute "bake": failed to open Kilnfile: open : no such file or directory

Previous versions of Kiln did not require a Kilnfile and the same bake command works with kiln v0.77.3. Was this an intentional change? I did not see any breaking changes in the release notes.

Reproduction steps

1. Attempt to build a tile without a kilnfile using kiln v0.79.0

2. Observe that building the tile fails when a Kilnfile is missing.

   $ kiln bake ...
   Warning: No credentials file found at ~/.kiln/credentials.yml. (hint: create this file to set default credentials. see --help for more info.)
   Warning: The "allow-only-publishable-releases" flag was not set. Some fetched releases may be intended for development/testing only. EXERCISE CAUTION WHEN PUBLISHING A TILE WITH THESE RELEASES!
   2023/04/04 10:33:54 could not execute "bake": failed to open Kilnfile: open : no such file or directory
   

Expected behavior

Expected either a breaking change in the release notes indicating this was an intentional change, or for the past behavior where tiles may continue to be built without Kilnfiles.

Additional context

Most of the internal VMware services teams that support tiles are not using Kilnfiles presently.