cmd/cue: pkg directory treated like cue.mod/{pkg,gen,usr}

[myitcv]

What version of CUE are you using (cue version)?

$ cue version
cue version +aa61ee7f linux/amd64

Does this issue reproduce with the latest release?

Yes

What did you do?

cd x
exec cue export x.cue

-- x/x.cue --
package x

import "example.com/component"

top: component.name
-- pkg/example.com/component/component.cue --
package component

name: "component"

What did you expect to see?

> exec cue export x.cue
[stderr]
import failed: cannot find package "example.com/component":
    ./x.cue:3:8

What did you see instead?

> exec cue export x.cue
[stdout]
{
    "top": "component"
}

Per @mpvl in #452 (comment) this is likely a legacy of pre-module support for imports.

We should drop support for this mechanism entirely in favour of modules.

cc @seh as a follow up to #452 (comment)

[cueckoo]

This issue has been migrated to cue-lang/cue#1014.

For more details about CUE's migration to a new home, please see cue-lang/cue#1078.