[improve] PIP-342: OTel client metrics support

[merlimat]

PIP: #22178

Motivation

Modifications

(Tests are still missing)

Verifying this change

• Make sure that the change passes the CI checks.

(Please pick either of the following options)

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

(or)

This change is already covered by existing tests, such as (please describe tests).

(or)

This change added tests and can be verified as follows:

(example:)

• Added integration tests for end-to-end deployment with large payloads (10MB)
• Extended integration test for recovery after broker failure

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

If the box was checked, please highlight the changes

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

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

Matching PR in forked repository

PR in forked repository:

[merlimat]

@asafm I applied most of the suggestion, please give it another pass

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 91.08434% with 37 lines in your changes are missing coverage. Please review.

Project coverage is 73.64%. Comparing base (bbc6224) to head (980bae3).
Report is 48 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #22179      +/-   ##
============================================
+ Coverage     73.57%   73.64%   +0.07%     
- Complexity    32624    32783     +159     
============================================
  Files          1877     1885       +8     
  Lines        139502   140057     +555     
  Branches      15299    15352      +53     
============================================
+ Hits         102638   103151     +513     
- Misses        28908    28930      +22     
- Partials       7956     7976      +20     

Flag	Coverage Δ
inttests	26.76% <60.96%> (+2.17%)	⬆️
systests	24.62% <54.93%> (+0.30%)	⬆️
unittests	72.89% <91.08%> (+0.05%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...va/org/apache/pulsar/client/api/ConsumerStats.java	0.00% <ø> (ø)
...va/org/apache/pulsar/client/api/ProducerStats.java	0.00% <ø> (ø)
.../pulsar/client/impl/BatchMessageContainerImpl.java	80.89% <100.00%> (ø)
...e/pulsar/client/impl/BinaryProtoLookupService.java	84.36% <100.00%> (+1.82%)	⬆️
...g/apache/pulsar/client/impl/ClientBuilderImpl.java	86.16% <100.00%> (+0.17%)	⬆️
.../java/org/apache/pulsar/client/impl/ClientCnx.java	71.98% <100.00%> (+0.20%)	⬆️
.../org/apache/pulsar/client/impl/ConnectionPool.java	76.44% <100.00%> (+1.92%)	⬆️
...va/org/apache/pulsar/client/impl/ConsumerImpl.java	77.96% <100.00%> (+0.39%)	⬆️
...ache/pulsar/client/impl/UnAckedMessageTracker.java	92.06% <100.00%> (+0.46%)	⬆️
...lsar/client/impl/conf/ClientConfigurationData.java	96.72% <100.00%> (+0.02%)	⬆️
... and 11 more

... and 74 files with indirect coverage changes

[lhotari]

LGTM, good work @merlimat

[asafm]

LGTM.