fix: honor NetworkHttpClient RequestConfig in makeRequest

[arimu1]

Fixes #913

NetworkHttpClient(RequestConfig) stores the caller's config on the Apache HttpClientBuilder via setDefaultRequestConfig, but makeRequest always called httpUriRequestBase.setConfig(DEFAULT_REQUEST_CONFIG). Per-request config wins in HttpClient 5, so custom timeouts (e.g. response timeout) were silently ignored.

Changes

• Store the constructor RequestConfig in a field (defaults to DEFAULT_REQUEST_CONFIG for the no-arg path).
• In makeRequest, apply this.requestConfig on each request instead of hardcoding DEFAULT_REQUEST_CONFIG.
• For NetworkHttpClient(HttpClientBuilder) (isCustomClient=true), skip per-request setConfig so builder-level defaults remain in effect.

Test plan

• mvn test -Dtest=NetworkHttpClientTest — 21 tests pass (JDK 17 / JBR 17.0.14, macOS darwin)
• New testMakeRequestUsesConstructorRequestConfig — verifies a custom RequestConfig (12345 ms response timeout) is applied on the executed HttpUriRequestBase
• New testCustomHttpClientBuilderDoesNotSetPerRequestConfig — verifies the HttpClientBuilder constructor path does not override per-request config
• Confirmed both new tests fail on unfixed main (constructor config replaced by DEFAULT_REQUEST_CONFIG; custom builder path incorrectly received default config)

Checklist

• I acknowledge that all my contributions will be made under the project's license
• I have made a material change to the repo (functionality, testing, spelling, grammar)
• I have read the Contribution Guidelines and my PR follows them
• I have titled the PR appropriately
• I have updated my branch with the main branch
• I have added tests that prove my fix is effective or that my feature works
• I have added the necessary documentation about the functionality in the appropriate .md file
• I have added inline documentation to the code I modified