v0.27.1 read_optimizer_stats breaks backwards compatibility

[GabrielKS]

The changes to OptimizerStats in 0d6f377 prevent calling read_optimizer_stats on results serialized with a previous version of PowerSimulations.

using PowerSimulations

res = get_decision_problem_results(SimulationResults("path/to/old/results"), "UC")
read_optimizer_stats(res)

The above works with v0.27.0. With v0.27.1 I get:

ERROR: LoadError: BoundsError: attempt to access 20-element Vector{Float64} at index [21]
Stacktrace:
  [1] getindex
    @ ./essentials.jl:13 [inlined]
  [2] PowerSimulations.OptimizerStats(data::Vector{Float64})
    @ PowerSimulations ~/Documents/JuliaProjects/S-PA-Entity-Metric/PowerSimulations.jl/src/core/optimizer_stats.jl:69
  [3] (::PowerSimulations.var"#305#306"{Matrix{Float64}})(i::Int64)
    @ PowerSimulations ./cartesian.jl:0
  [4] iterate
    @ ./generator.jl:47 [inlined]
  [5] collect(itr::Base.Generator{Base.OneTo{Int64}, PowerSimulations.var"#305#306"{Matrix{Float64}}})
    @ Base ./array.jl:834
  [6] read_optimizer_stats(store::PowerSimulations.HdfSimulationStore, model_name::Symbol)
    @ PowerSimulations ~/Documents/JuliaProjects/S-PA-Entity-Metric/PowerSimulations.jl/src/simulation/hdf_simulation_store.jl:234
  [7] _read_optimizer_stats
    @ ~/Documents/JuliaProjects/S-PA-Entity-Metric/PowerSimulations.jl/src/simulation/decision_model_simulation_results.jl:633 [inlined]
  [8] #376
    @ ~/Documents/JuliaProjects/S-PA-Entity-Metric/PowerSimulations.jl/src/simulation/simulation_problem_results.jl:609 [inlined]
  [9] open_store(func::PowerSimulations.var"#376#377"{…}, ::Type{…}, directory::String, mode::String; filename::String)
    @ PowerSimulations ~/Documents/JuliaProjects/S-PA-Entity-Metric/PowerSimulations.jl/src/simulation/hdf_simulation_store.jl:108
 [10] open_store
    @ ~/Documents/JuliaProjects/S-PA-Entity-Metric/PowerSimulations.jl/src/simulation/hdf_simulation_store.jl:98 [inlined]
 [11] _read_optimizer_stats
    @ ~/Documents/JuliaProjects/S-PA-Entity-Metric/PowerSimulations.jl/src/simulation/simulation_problem_results.jl:604 [inlined]
 [12] read_optimizer_stats(res::PowerSimulations.SimulationProblemResults{…}; store::Nothing)
    @ PowerSimulations ~/Documents/JuliaProjects/S-PA-Entity-Metric/PowerSimulations.jl/src/simulation/simulation_problem_results.jl:600
 [13] read_optimizer_stats(res::PowerSimulations.SimulationProblemResults{PowerSimulations.DecisionModelSimulationResults})
    @ PowerSimulations ~/Documents/JuliaProjects/S-PA-Entity-Metric/PowerSimulations.jl/src/simulation/simulation_problem_results.jl:595
 [14] top-level scope
    @ ~/Documents/JuliaProjects/S-PA-Entity-Metric/PowerAnalytics-demos/~optimizer_stats_bug_repro.jl:4
 [15] include(fname::String)
    @ Base.MainInclude ./client.jl:489
 [16] top-level scope
    @ REPL[3]:1

[GabrielKS]

(the commit I added there was named incorrectly, it is not relevant)