build(snap): source metadata from central repo

[MonicaisHer]

The metadata kept in snapcraft.yaml is obsolete because it is being overridden on the store. This change will allow sourcing the central copy of metadata.

See canonical/edgex-snap-metadata#2

Signed-off-by: Mengyi Wang mengyi.wang@canonical.com

If your build fails due to your commit message not passing the build checks, please review the guidelines here: https://github.com/edgexfoundry/edgex-cli/blob/main/.github/Contributing.md

PR Checklist

Please check if your PR fulfills the following requirements:

• I am not introducing a breaking change (if you are, flag in conventional commit message with BREAKING CHANGE: describing the break)
• I am not introducing a new dependency (add notes below if you are)
• I have added unit tests for the new feature or bug fix (if not, why?)
• I have fully tested (add details below) this the new feature or bug fix (if not, why?)
• I have opened a PR for the related docs change (if not, why?)

Testing Instructions

# clean and build:
$ snapcraft clean && snapcraft

# unpack the built snap:
$ unsquashfs name.snap

# verify that icon exists:
$ ls squashfs-root/meta/gui/icon.png 
squashfs-root/meta/gui/icon.png

# verify that version, summary and description are included
$ cat squashfs-root/meta/snap.yaml
name: edgex-cli
version: 2.0.0-dev.20
summary: EdgeX CLI
description: |-
  EdgeX CLI is a command-line interface tool for developers, used for interacting with the EdgeX microservices.

  For a graphical user interface, see https://snapcraft.io/edgex-ui

  **Snap usage instructions**

  https://github.com/edgexfoundry/edgex-cli/blob/main/snap/README.md

  **Source code and more info**

  https://github.com/edgexfoundry/edgex-cli

  **Getting started**

  * v1.3: https://docs.edgexfoundry.org/1.3/getting-started/tools/Ch-CommandLineInterface
  * v2.1: https://docs.edgexfoundry.org/2.1/getting-started/tools/Ch-CommandLineInterface
  * v2.2: https://docs.edgexfoundry.org/2.2/getting-started/tools/Ch-CommandLineInterface

  **EdgeX Documentation**

  https://docs.edgexfoundry.org

  **Reference platform snap**

  https://snapcraft.io/edgexfoundry

...

New Dependency Instructions (If applicable)

[farshidtz]

Tested and the metadata is correctly pulled from the AppStream source.

Thanks.

[siggiskulason]

LGTM