This change adds the groovy step writeTemporaryCredentials, in order to
avoid resolving configuration parameters within the piperPipelineStageIntegration
in the future.
For the integration tests functionality provided by the SAP Cloud SDK
Pipeline it needs be possible to configure a credential id pointing to
Jenkins credentials, which are then temporarily written to a file to be
available during the execution of the integration tests.
With the previous implementation solely in the TemporaryCredentialsUtils
class, it would be required to resolve the credentialId from the
configuratuion within the piperPipelineStageIntegration, once we fully
migrate the Cloud SDK integration tests stage.
