Function inc_n_rpc_requests_started

pub fn inc_n_rpc_requests_started(
    n: u64,
    client: impl Into<MetricLabelValue>,
    method: impl Into<MetricLabelValue>,
    contract: impl Into<MetricLabelValue>,
    function: impl Into<MetricLabelValue>,
    req_type: impl Into<MetricLabelValue>,
)

Add n to rpc_requests_started counter.