Upgrade Step for Link-Layer Devices Named "unsupportedx"

[manadart]

Description of change

This patch adds an upgrade step for version 2.8.1 that removes link-layer data for devices sourced from the EC2 provider with names beginning with "unsupported".

Such devices and addresses duplicate correctly named data sourced directly from the machine, and prevent updates via the new instance-poller logic.

At the same time, the 2.8.0 step for updating address origin is repeated, as this version had a subsequently fixed issue whereby addresses could achieve an empty origin value, regressing the step.

QA steps

• Bootstrap to AWS with any prior version; I used 2.7 edge.
• Connect to Mongo and observe entries in the linklayerdevices and ip.addresses collections with names beginning with "unsupported".
• With this patch, run juju upgrade-controller --build-agent.
• Check the collections again to ensure that the unsupported devices and addresses are absent.
• Note also the "provider" origin on docs in the ip.addresses collection, where it was absent before.

Documentation changes

None

Bug reference

N/A

[manadart]

Add upgrade step for removing "unsupportedx" AWS link-layer devices.

[manadart]

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