Add all-clusters-app example support to mbed platform.

[lukgni]

The all-clusters-app works in very similiar way to mbed lock-app and lighting-app examples. The only difference here is that all-clusters-app supports all ZCL clusters by defining general stubs in all-clusters-common directory.

Because this example will be used mainly for testing ZCL clusters messages support, there is no need for handling user buttons in the same way how it is done in lock/lighting app examples (at least for now).

However, status led functionality has been left unchanged - just for easy indication about BLE advertising/pairing and WIFI connection status.

Change set:

• Adding all-clusters-app example sources for mbed
• Update task/launch.json with new entry
• Update mbed_examples.yml github workflow with new entry

[pan-]

Can you rebase the branch @lukgni, the CI and build helper files have been updated.

[lukgni]

Can you rebase the branch @lukgni, the CI and build helper files have been updated.

Done.