Function invoke_provider_method 

async fn invoke_provider_method(
    environment: &MountainEnvironment,
    registration: &ProviderRegistrationDTO,
    method: &str,
    arguments: Vec<Value>,
) -> Result<Value, CommonError>

Like invoke_provider but uses an explicit method name instead of the $provide{ProviderType} convention. Used for prepare steps ($prepareCallHierarchyItems, $prepareTypeHierarchyItems) where the method prefix differs from the provider type string.