Jersey2: Do not reinitialize ClientConfig with default values when building HTTP Client

[jheyens]

#8756 fixed issue #8755, where enabling debug settings in the ApiClient had no effect since the HTTP client was not reinitialized. The fix was to always reinitialize the HTTP client. This fix causes another issue, however, since the HTTP client is always reinitialized from the default settings, ignoring previously set options via apiClient#setClientConfig(ClientConfig) (e.g. proxy settings).

This PR fixes both issues by applying debug settings to the existing ClientConfig instead of always reinitializing from default settings.

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@bbdouglas @sreeshas @jfiala @lukoyanov @cbornet @jeff9finger @karismann @Zomzog @lwlee2608 @martin-mfg

[jheyens]

I also applied the changes to Jersey3 (even though you only asked me to in the #20688).

[martin-mfg]

I also applied the changes to Jersey3 (even though you only asked me to in the #20688).

Good point, thanks!