Fix java rest client ApiClient template to properly assign ObjectMapper

[CaptainAye]

Description:
The changes fix the ApiClient mustache template for java RestClient generator. Some of the constructors didn't properly pass the ObjectMapper parameter on, leading to creating default mapper even if the consumer passed custom instance.
Additionally, PR refactors the ApiClient constructors in order to move the creation logic to the one, most specific, constructor.

The pr fixes OpenAPITools#19667

Technical committee Java:
@martin-mfg, @lwlee2608, @Zomzog, @karismann, @jeff9finger, @cbornet, @lukoyanov, @jfiala, @sreeshas, @bbdouglas

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