Plugin broker should be able to send warning about plugins configuration to WS master

[garagatyi]

Description

Plugin registry notation changes will introduce field deprecated into meta.yaml:

publisher: plugin_publisher
id: plugin_id
version: 1.2.3
name: Some plugin
deprecate:
   autoMigrate: true
   migrateTo: another_publisher/another_plugin_id:1.0.0

See explanation here eclipse-che/che-plugin-registry#55 (comment)

Plugin broker should send a warning when plugin with deprecated section is being processed to WS master.
WS master than should add it to the workspace runtime warnings.
And UD will be able to show it to the user.
Apart from that, broker should send brokering log about that, so user would be able to see it when workspace is starting.

Implementation details:
At the moment broker sends JSON list to WS master with Che plugins descriptions.

1. We need to change that to an object that contains field warnings. And add above described warning to this field.
2. WS master should add to workspace runtime warnings that come from plugin broker.

[che-bot]

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[amisevsk]

I believe this will be resolved in a different way in eclipse-che/che-plugin-registry#228

Leaving open as we should decide if this is sufficient of if the broker should do additional work

[amisevsk]

/remove-lifecycle stale

[che-bot]

Issues go stale after 180 days of inactivity. lifecycle/stale issues rot after an additional 7 days of inactivity and eventually close.

Mark the issue as fresh with /remove-lifecycle stale in a new comment.

If this issue is safe to close now please do so.

Moderators: Add lifecycle/frozen label to avoid stale mode.

[amisevsk]

/remove-lifecycle stale