Introduced service time metrics to OpenSearch-Py client.

[saimedhi]

Description

Introduced service time metrics to OpenSearch-Py client.

Issues Resolved

678

• [x] Added tests
• [ ] Guide to be added
• [ ] Service time metrics will be implemented for AsyncOpensearch in a subsequent PR

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[codecov[bot]]

Codecov Report

Attention: Patch coverage is 65.78947% with 26 lines in your changes are missing coverage. Please review.

Project coverage is 71.91%. Comparing base (ba715b9) to head (5247b67).

:exclamation: Current head 5247b67 differs from pull request most recent head a625715. Consider uploading reports for the commit a625715 to get more accurate results

Files	Patch %	Lines
opensearchpy/metrics/metrics_events.py	48.48%	17 Missing :warning:
opensearchpy/metrics/metrics.py	76.19%	5 Missing :warning:
opensearchpy/connection/http_requests.py	66.66%	2 Missing :warning:
opensearchpy/connection/http_urllib3.py	66.66%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #716 +/- ## ========================================== - Coverage 71.95% 71.91% -0.05% ========================================== Files 91 94 +3 Lines 8001 8085 +84 ========================================== + Hits 5757 5814 +57 - Misses 2244 2271 +27 ```

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[saimedhi]

The failing tests are not related to this PR but are caused by recent changes to the OpenSearch API Specification, which is now natively written in OpenAPI. The generator and developer guide will be fixed accordingly in an upcoming PR.

[saimedhi]

@VachaShah please take a look

[saimedhi]

Ready for review