Avoid duplicate countitems metrics

[francoisferrand]

Metrics from both workers & managers are instantiated in both kind of
processes, leading to duplicates when merging (naively) the metrics.

Improving merge is not trivial, for now we simply are more careful about
instantiating the metrics: bucketProcessingDuration and
consolidationDuration are only instantiated on master process. Since
they have labels, bucketsCount and objectsCount are not affected, so
we can keep them as is for now (since they are used directly from
S3UtilsMongoClient, and would need a significant refactor to make it
work both in prod and tests).

Issue: S3UTILS-175

[bert-e]

Hello francoisferrand,

My role is to assist you with the merge of this
pull request. Please type @bert-e help to get information
on this process, or consult the user documentation.

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[bert-e]

Request integration branches

Waiting for integration branch creation to be requested by the user.

To request integration branches, please comment on this pull request with the following command:

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Alternatively, the /approve and /create_pull_requests commands will automatically
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[francoisferrand]

/approve

[bert-e]

Build failed

The build for commit did not succeed in branch w/1.15/bugfix/S3UTILS-175.

The following options are set: approve

[bert-e]

I have successfully merged the changeset of this pull request
into targetted development branches:

• ✔️ development/1.14

• ✔️ development/1.15

The following branches have NOT changed:

• development/1.13
• development/1.4

Please check the status of the associated issue S3UTILS-175.

Goodbye francoisferrand.

The following options are set: approve