Add logging with state to Bayesian Optimizer

[adrianmolzon]

Hey all, long time listener first time contributor. I've created two new methods for the BayesianOptimizer class to allow users to save and load their optimizers while maintaining state. I've added a new section to the basic tour to demonstrate this cleaner method for saving and loading their optimizer.

A couple notes, users using a custom acquisition function will have to write their own get_acquisition_params and set_acquisition_params class functions in order to preserve exact state, otherwise there might be a loss of state when saving and loading. This should still be strictly better than the previous flow for saving and loading optimizers which ignored the acquisition parameters.

If this pull request gets merged into master, I'd like to remove the previous saving methodology, but I'll save that for a future PR.

[adrianmolzon]

@till-m

[till-m]

@adrianmolzon I realized the coverage bot is broken, so let me fix that first before moving on with this PR

[till-m]

Generally looks good, especially the extensive testing. I added a few comments here and there.

I think the old save/load functionality should be removed, it's better not to have multiple ways to do the same thing, especially if one of them is clearly superior.

[codecov]

Codecov Report

Attention: Patch coverage is 97.91667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 96.43%. Comparing base (aed6a25) to head (472fd93).
Report is 23 commits behind head on master.

Files with missing lines	Patch %	Lines
bayes_opt/acquisition.py	96.36%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #547      +/-   ##
==========================================
+ Coverage   96.19%   96.43%   +0.24%     
==========================================
  Files          10       12       +2     
  Lines         867     1235     +368     
==========================================
+ Hits          834     1191     +357     
- Misses         33       44      +11     

☔ 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.

[till-m]

I think this is ready to go, I will merge this in the coming days if there are no objections.

[till-m]

Thanks for your contribution!