Improve logs, handling and parsing of Helm install erros

Currently, if the `helm install` fails for some reason (e.g syntax errors on generated manifests) then Onyxia-API logs a "generic" error with the Java stacktrace that contains almost no real info :
`[onyxia-api-8b8497478-wdm5l] {"@timestamp":"2024-12-12T13:41:13.583714227Z","@version":"1","message":"Servlet.service() for servlet [dispatcherServlet] in context with path [\/api] threw exception","logger_name":"org.apache.catalina.core.ContainerBase.[Tomcat].[localhost].[\/api].[dispatcherServlet]","thread_name":"http-nio-8080-exec-3","level":"ERROR","level_value":40000,"stack_trace":"com.fasterxml.jackson.databind.exc.MismatchedInputException: No content to map due to end-of-input\n at [Source: REDACTED (`StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION` disabled); line: 1]\n\tat com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:59)\n\tat com.fasterxml.jackson.databind.ObjectMapper._initForReading(ObjectMapper.java:5008)\n\tat ...
[TRIMMED FOR CLARITY]"}
`
and in a separate message the real helm error as emitted by the helm process :
`[onyxia-api-8b8497478-wdm5l] Error: YAML parse error on argo-workflows/templates/networkpolicy-ingress.yaml: error converting YAML to JSON: yaml: line 10: did not find expected '-' indicator`
This one is much more relevant and is currently redirected directly to System.err (see https://github.com/InseeFrLab/onyxia-api/blob/715cda25520e83a6e79308c0cefe837e1b1d8698/helm-wrapper/src/main/java/io/github/inseefrlab/helmwrapper/utils/Command.java#L27)
which is not properly integrated with the rest of logging system (e.g it does not use json structuring)

We should catch the real error instead of redirecting it to System.err