cue/interpreter/embed: support embed attribute appearing multiple times for single field declaration?

[myitcv]

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

$ cue version
cue version v0.0.0-20240712164527-719893f23850

go version go1.22.3
      -buildmode exe
       -compiler gc
  DefaultGODEBUG httplaxcontentlength=1,httpmuxgo121=1,tls10server=1,tlsrsakex=1,tlsunsafeekm=1
     CGO_ENABLED 1
          GOARCH arm64
            GOOS linux
             vcs git
    vcs.revision 719893f23850172d224720e6d1257586179ac895
        vcs.time 2024-07-12T16:45:27Z
    vcs.modified false
cue.lang.version v0.10.0

Does this issue reproduce with the latest release?

Yes

What did you do?

env CUE_EXPERIMENT=embed
exec cue export x.cue
cmp stdout stdout.golden

-- x.cue --
@extern(embed)

package x

f: _ @embed(glob=*.json) @embed(glob=*.yaml)

-- x.json --
5

-- x.yaml --
test

-- stdout.golden --
{
    "f": {
        "x.json": 5,
        "x.yaml": "test"
    }
}

What did you expect to see?

Passing test, at least based on the conversations we had regarding #3264 that I recall.

What did you see instead?

> env CUE_EXPERIMENT=embed
> exec cue export x.cue
[stderr]
duplicate @embed attributes:
    ./x.cue:5:26
[exit status 1]
FAIL: /tmp/testscript174121000/repro.txtar/script.txtar:2: unexpected command failure

[myitcv]

The workaround for now is to declare the field multiple times:

env CUE_EXPERIMENT=embed
exec cue export x.cue
cmp stdout stdout.golden

-- x.cue --
@extern(embed)

package x

f: _ @embed(glob=*.json)
f: _ @embed(glob=*.yaml)

-- x.json --
5

-- x.yaml --
test

-- stdout.golden --
{
    "f": {
        "x.json": 5,
        "x.yaml": "test"
    }
}