Introduced service time metrics to OpenSearch-Py client.

[saimedhi]

Description

Introduced service time metrics to OpenSearch-Py client.

Issues Resolved

#678

Guide and Tests need to be added for this change.

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[codecov]

Codecov Report

Attention: Patch coverage is 65.21739% with 24 lines in your changes are missing coverage. Please review.

Project coverage is 72.06%. Comparing base (4b69c09) to head (5ea57d3).
Report is 2 commits behind head on main.

Files	Patch %	Lines
opensearchpy/metrics.py	60.00%	16 Missing ⚠️
opensearchpy/connection/http_requests.py	66.66%	3 Missing ⚠️
opensearchpy/connection/http_urllib3.py	66.66%	3 Missing ⚠️
opensearchpy/transport.py	77.77%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #689      +/-   ##
==========================================
- Coverage   72.14%   72.06%   -0.08%     
==========================================
  Files          89       90       +1     
  Lines        7945     8009      +64     
==========================================
+ Hits         5732     5772      +40     
- Misses       2213     2237      +24     

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[saimedhi]

I'm unsure about my changes to async connections. I've tested them, but I'm uncertain if I've covered all cases. Let's start by applying these changes for requests and urllib3 connections first. For async connections, I'll need to review whether a similar approach to sync connections is suitable or if we should utilize something like aiohttptraceconfig.

I've created a copy of my tested and functional changes, which include async connections. However, I'm streamlining this PR to concentrate solely on sync connections.

[dblock]

Good start. The if calculate_service_time: is the anti-pattern we need to fix here and make it more object-oriented. Define a generic Metrics interface with methods such as request_start, and a specific implementation for it using Events, e.g. EventsMetrics. See below.

[dblock]

Better. Needs tests and some more changes.