refs https://forum.ghost.org/t/admin-template-issues-default-install/31750
- we recently switched to using different folders within `core/built`, to
indicate the assets that are applicable for development/production
environments
- unfortunately, this came with the side effect of the "development" assets
missing in the published tarball, which meant Admin wouldn't load when
running in development mode
- this was a regression from how it previously worked because we used to
just copy the production HTML file to the development HTML name, and
use the same assets
- after thinking about it, I think we can get rid of the split folders
for assets, because I don't think the use-case is there for having
them:
- if you run Ghost from source, you're 99% only using the
development-built assets
- if you want production ones, you can run with a flag, but the
development ones get wiped anyway
- those running Ghost from a published package are using the same
assets and HTML file
- therefore, I think we can make our lives simpler by removing the env
folders and using a folder under `core/built/admin/...`
- this commit implements that across Ghost and Admin
7cf4f595f7