Find a good way to test results for multi-period AC power flow calculation

[rbolgaryn]

The easiest way would be to fully implement the calculation using the time series data in sys.

Best to test results using two different approaches.

Refers to this test:

@testset "MULTI-PERIOD power flows evaluation: NR" for ACSolver in
                                                       (
    NLSolveACPowerFlow,
    KLUACPowerFlow,
    PowerFlows.LUACPowerFlow,
)
    # get system
    sys = PSB.build_system(PSB.PSITestSystems, "c_sys14"; add_forecasts = false)

    # create structure for multi-period case
    pf = ACPowerFlow(ACSolver)
    time_steps = 24
    data = PowerFlowData(pf, sys; time_steps = time_steps)

    # allocate timeseries data from csv
    prepare_ts_data!(data, time_steps)

    # get power flows with NR KLU method and write results
    solve_powerflow!(data; pf = pf)

    # check results
    # for t in 1:length(data.timestep_map)
    #     res_t = solve_powerflow(pf, sys, t)  # does not work - ts data not set in sys
    #     flow_ft = res_t["flow_results"].P_from_to
    #     flow_tf = res_t["flow_results"].P_to_from
    #     ts_flow_ft = results[data.timestep_map[t]]["flow_results"].P_from_to
    #     ts_flow_tf = results[data.timestep_map[t]]["flow_results"].P_to_from
    #     @test isapprox(ts_flow_ft, flow_ft, atol = 1e-9)
    #     @test isapprox(ts_flow_tf, flow_tf, atol = 1e-9)
    # end
end