Request response client: acquire event loop group

[xiazhvera]

Issue #, if available:

Description of changes:
Acquire event loop for rr_client.

In the previous implementation, releasing of the protocol client would potentially release the event loop group if no other component acquire the event loop group. This would cause a race condition where the rr_client or streaming operation is trying to use the event loop to process its tasks while the event loop has already be released. We fixed it by acquire the event loop group for rr client.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 42.85714% with 4 lines in your changes missing coverage. Please review.

Project coverage is 84.63%. Comparing base (235f560) to head (7e230c2).

Files with missing lines	Patch %	Lines
source/request-response/request_response_client.c	42.85%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #392      +/-   ##
==========================================
- Coverage   84.66%   84.63%   -0.03%     
==========================================
  Files          25       25              
  Lines       10483    10489       +6     
==========================================
+ Hits         8875     8877       +2     
- Misses       1608     1612       +4     

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