Fix initialization of JWKs client per request

[ldclakmal]

Description:
The HTTP client used to call the JWKs endpoint (when the JWT signature is need to be validated with the use of JWK) is initialized for each request with the provided client configurations. This ends up with a Netty error message when doing a load test. error: failed to create a child event loop. This issue was identified from the MGW 3.2.0.

Describe your solution(s)
This approach can be improved by initializing the client once for the inbound JWT auth provider.

[github-actions]

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      - Reason/EngineeringMistake - The issue occurred due to a mistake made in the past.
      - Reason/Regression - The issue has introduced a regression.
      - Reason/MultipleComponentInteraction - Issue occured due to interactions in multiple components.
      - Reason/Complex - Issue occurred due to complex scenario.
      - Reason/Invalid - Issue is invalid.
      - Reason/Other - None of the above cases.