Add Java 25 support

[bobbrodie]

The SDK compiles on Java 25 (I use Corretto), but running mvn clean test fails with the following:

[ERROR] Errors: 
[ERROR]   ClientTest.it_should_provide_client_by_config:146 » BitPayGeneric When trying to load private key. Make sure the configuration details are correct and the private key and tokens are valid :  (No such file or directory)
[ERROR]   ClientTest.it_should_provide_client_by_config_with_platform_info_header:159 » BitPayGeneric When trying to load private key. Make sure the configuration details are correct and the private key and tokens are valid :  (No such file or directory)

We should investigate and prepare for Java 25 in v10.3.0.