chore(mbeans): adjust MBeanMetrics GraphQL query for updated schema

[andrewazores]

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Depends on https://github.com/cryostatio/cryostat3/pull/307 Based on #1218

Description of the change:

Adjusts GraphQL queries for the updated schema in 3.0 where the mbeanMetrics subquery is nested under the Target object, not under the TargetNode (the DiscoveryNode which the Target belongs to). Adjusts the client's data model to always expect labels and annotations on Targets returned from the API, whether GraphQL or plain HTTP, and for both labels and annotations to use the new "key-value list" format.

Motivation for the change:

Restores the web UI's ability to retrieve MBean Metrics for the Dashboard and Topology, as seen in the screenshot below.

How to manually test:

1. Run CRYOSTAT_IMAGE=quay.io... sh smoketest.sh...
2. ...

[github-actions[bot]]

This PR/issue depends on:

• cryostatio/cryostat3#307
• cryostatio/cryostat-web#1218 By Dependent Issues (🤖). Happy coding!

[andrewazores]

/build_test

[github-actions[bot]]

Test image available:

CRYOSTAT_IMAGE=ghcr.io/cryostatio/cryostat-web:pr-1219-a37abbbbc1d1c339103ae1fdfc8426e115808ca1 bash smoketest.bash # then open http://localhost:8080

[andrewazores]

Not sure why the diff here is including https://github.com/cryostatio/cryostat-web/pull/1216 as part of the commit set. That's already merged into main which this is based on top of, but I guess something about the unmerged upstream cryostat3-graphql branch is confusing GitHub's UI.