[fix][broker] Fixed reset for AggregatedNamespaceStats

[asafm]

Motivation

AggregatedNamespaceStats is the object used when topic-level metrics are aggregated into namespace level, specifically when exposeTopicLevelMetricsInPrometheus=false.
There is a loop which runs over all namespaces, and for each one, the same object is used, by first resetting it and then adding each topic metrics to it.
The existing reset() method lacks all fields hence some fields were accumulating over round of metrics reporting to prometheus metrics servlet, good example for it would be pulsar_out_bytes_total.

Modifications

I've fixed AggregatedNamespaceStats.reset() by including all the fields that were missing from it.

Verifying this change

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This change added tests and can be verified as follows:

• Added testReset() method. I may add in subsequent PR a more generic way to validate we never forget to reset an added field.

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

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• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
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• The admin CLI options
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• Anything that affects deployment

Documentation

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Matching PR in forked repository

PR in forked repository: asafm#3

[github-actions]

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[codelipenghui]

LGTM, left some minor comments.

[codelipenghui]

/pulsarbot run-failure-checks

[codelipenghui]

/pulsarbot run-failure-checks