oe-setup-layers: support inline URI

oe-setup-layers: support inline URI

Most of the time, when we describe a remote, the layer data (also used by
the script bitbake-setup) looks like this:

"bitbake": {
    "git-remote": {
        "remotes": {
            "origin": {
                "uri": "https://git.openembedded.org/bitbake"
            }
        },
        ...
    }
}

i.e. an URI with the common name 'origin'. Alternatively, we could simplify this, by
using a shorter structure with the property 'uri' only:

"bitbake": {
    "git-remote": {
        "uri": "https://git.openembedded.org/bitbake

",
        ...
    }
}

These properties can be used together.

Signed-off-by: Corentin Guillevic <corentin.guillevic@smile.fr>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>