Fix creating system images

[ptsavol]

Fixes two bugs in sysimage creation:

• Call Pkg.add() for all entries in loaded_modules.txt but catch a Pkg.Types.PkgError exception so that modules are skipped and only actual packages are installed. This fixes sysimage creation for Julia 1.9+ which introduced Extensions.
• Do not Pkg.add() packages that have been installed already. This fixes sysimage creation for development packages.

Re spine-tools/Spine-Toolbox#2451

Checklist before merging

• [ ] Documentation (also in Toolbox repo) is up-to-date
• [ ] Release notes in Toolbox repo have been updated
• [ ] Unit tests have been added/updated accordingly
• [ ] Code has been formatted by black
• [x] Unit tests pass

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (082ca23) 60.25% compared to head (e9b9de1) 60.28%. Report is 2 commits behind head on 0.8-dev.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## 0.8-dev #180 +/- ## =========================================== + Coverage 60.25% 60.28% +0.02% =========================================== Files 194 194 Lines 17687 17687 Branches 2887 2887 =========================================== + Hits 10658 10662 +4 + Misses 6462 6458 -4 Partials 567 567 ```

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[ptsavol]

Commit f8e4592 makes a syimage file successfully but when I try to use the sysimage while running the tool, it gives me this Traceback. I don't know how to fix it so I'll try something else next.

julia> # Running julia run_spineopt.jl http://127.0.0.1:55331 http://127.0.0.1:55334
2-element Vector{String}:
 "http://127.0.0.1:55331"
 "http://127.0.0.1:55334"

Execution started at 2023-12-20T16:48:13.170
Preparing SpineOpt for sqlite:///C:\data\SpineToolboxData\Projects\SpineOptProject_III_0.8-dev\.spinetoolbox\items\input\input.sqlite...
Initializing data structure from db...
ERROR: LoadError: MethodError: no method matching getindex(::Module, ::String)
Stacktrace:
  [1] difference(left::Module, right::Module)
    @ SpineInterface C:\Users\ttepsa\.julia\packages\SpineInterface\CNP7u\src\api\core.jl:625
  [2] macro expansion
    @ C:\Users\ttepsa\.julia\packages\SpineOpt\ifkx1\src\run_spineopt.jl:239 [inlined]
  [3] macro expansion
    @ .\timing.jl:273 [inlined]
  [4] macro expansion
    @ C:\Users\ttepsa\.julia\packages\SpineOpt\ifkx1\src\util\misc.jl:51 [inlined]
  [5] prepare_spineopt(url_in::String; upgrade::Bool, log_level::Int64, filters::Dict{String, String})
    @ SpineOpt C:\Users\ttepsa\.julia\packages\SpineOpt\ifkx1\src\run_spineopt.jl:230
  [6] _run_spineopt(url_in::String, url_out::String; upgrade::Bool, mip_solver::Nothing, lp_solver::Nothing, add_user_variables::Function, add_constraints::Function, log_level::Int64, optimize::Bool, update_names::Bool, alternative::String, write_as_roll::Int64, use_direct_model::Bool, filters::Dict{String, String}, resume_file_path::Nothing)
    @ SpineOpt C:\Users\ttepsa\.julia\packages\SpineOpt\ifkx1\src\run_spineopt.jl:186
  [7] run_spineopt(url_in::String, url_out::String; upgrade::Bool, mip_solver::Nothing, lp_solver::Nothing, add_user_variables::Function, add_constraints::Function, log_level::Int64, optimize::Bool, update_names::Bool, alternative::String, write_as_roll::Int64, use_direct_model::Bool, filters::Dict{String, String}, log_file_path::Nothing, resume_file_path::Nothing)
    @ SpineOpt C:\Users\ttepsa\.julia\packages\SpineOpt\ifkx1\src\run_spineopt.jl:98
  [8] run_spineopt(url_in::String, url_out::String)
    @ SpineOpt C:\Users\ttepsa\.julia\packages\SpineOpt\ifkx1\src\run_spineopt.jl:79
  [9] top-level scope
    @ C:\Users\ttepsa\.spinetoolbox\work\run_spineopt__b76fd529445448d3b1b00ce904728841__toolbox\run_spineopt.jl:3
 [10] include(fname::String)
    @ Base.MainInclude .\client.jl:478
 [11] top-level scope
    @ none:1
in expression starting at C:\Users\ttepsa\.spinetoolbox\work\run_spineopt__b76fd529445448d3b1b00ce904728841__toolbox\run_spineopt.jl:3