Update problem plot for the MultiFittingProblem

[NicolaCourtier]

Description

Add a domain to the MultiFittingProblem to enable plotting with the standard quick plot. Also enable plotting of simulations that terminate early.

Issue reference

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Review

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• Updated the CHANGELOG.md in reverse chronological order (newest at the top) with a concise description of the changes, including the PR number.
• Noted any breaking changes, including details on how it might impact existing functionality.

Type of change

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• Examples: A change to existing or additional examples.
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• Added tests that prove my fix is effective or that my feature works.
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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.22%. Comparing base (114770e) to head (d25f116).
Report is 8 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #602   +/-   ##
========================================
  Coverage    99.22%   99.22%           
========================================
  Files           62       62           
  Lines         4498     4504    +6     
========================================
+ Hits          4463     4469    +6     
  Misses          35       35           

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[BradyPlanden]

LGTM - just one suggested change. Thanks @NicolaCourtier!