[FLINK-29623][Metrics][Prometheus] Update Prometheus Java Client to 0.16.0

[MartijnVisser]

What is the purpose of the change

• Flink uses an old and no longer supported version of io.prometheus:simpleclient. We should upgrade to the latest version

Brief change log

• Updated POM and NOTICE files

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): yes
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

[flinkbot]

CI report:

• 501fef3 Azure: SUCCESS

Bot commands

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[zentol]

This is at this time intentional; last time I looked into it I found that they changed the data model and we should look at the ramifications of that first before bumping anything.

[MartijnVisser]

last time I looked into it I found that they changed the data model and we should look at the ramifications of that first before bumping anything.

They've made such a change in their 0.10 version:

[CHANGE] Switch data model to OpenMetrics. Primarily this means that _total if present is stripped from the metric name of counters, and _total is now always a suffix on the sample value. This means that all Counter samples now have a _total suffix (prometheus/client_java#615)
[CHANGE] The io.prometheus.client.Collector.Type enum' value UNTYPED renamed to UNKNOWN (prometheus/client_java#615)

We should actually check if there are proper tests for this too.