Profile: add multistart optimization for profile points

[Doresic]

I added multistart optimization at each profile point.

Additional starts are sampled around the point suggested by profile_next_guess, and the original suggested start is always included as well. Failed starts are tolerated, and the best finite result is kept.

I also added warnings when profiling finds lower function values than the supplied optimum, and when non-profiled parameters hit bounds during profiling.

Also:

• add profile_n_starts and profile_sampling_sigma to ProfileOptions
• use multistart optimization during profile walking
• extend the related profiling tests

Open question: when non-profiled parameters hit bounds during profiling, should we eventually support relaxing those bounds (of the parameters we're not profiling), or is warning-only the better behavior here? Allowing a relaxation of the bounds would make the plots actually show non-identifiable parameters when they are such. But we might risk some weird optimisation failures in some unusual cases.

Should be merged only after #1711 -- contains all changes of that PR currently, too.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

❌ Patch coverage is 87.75510% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.37%. Comparing base (7255fc7) to head (0f84792).

Files with missing lines	Patch %	Lines
pypesto/profile/profile.py	72.72%	3 Missing ⚠️
pypesto/profile/walk_along_profile.py	90.62%	3 Missing ⚠️
❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1712      +/-   ##
===========================================
+ Coverage    84.35%   84.37%   +0.01%     
===========================================
  Files          164      164              
  Lines        14752    14799      +47     
===========================================
+ Hits         12444    12486      +42     
- Misses        2308     2313       +5     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.