Slight rewrite of update_g and update_fg as well as some SAMIN fixes

[pkofod]

No description provided.

[github-actions]

Benchmark Results

	master	ba54d7c...	master / ba54d7c...
multivariate/solvers/first_order/AdaMax	0.646 ± 0.0076 ms	0.645 ± 0.0078 ms	1
multivariate/solvers/first_order/Adam	0.647 ± 0.0079 ms	0.644 ± 0.0078 ms	1.01
multivariate/solvers/first_order/BFGS	0.223 ± 0.006 ms	0.224 ± 0.0048 ms	0.998
multivariate/solvers/first_order/ConjugateGradient	0.0477 ± 0.00061 ms	0.048 ± 0.00069 ms	0.993
multivariate/solvers/first_order/GradientDescent	1.71 ± 0.018 ms	1.71 ± 0.015 ms	1
multivariate/solvers/first_order/LBFGS	0.219 ± 0.004 ms	0.219 ± 0.004 ms	1
multivariate/solvers/first_order/MomentumGradientDescent	2.51 ± 0.02 ms	2.5 ± 0.019 ms	1
multivariate/solvers/first_order/NGMRES	0.553 ± 0.011 ms	0.553 ± 0.01 ms	1
time_to_load	0.547 ± 0.0091 s	0.538 ± 0.0016 s	1.02

Benchmark Plots

A plot of the benchmark results have been uploaded as an artifact to the workflow run for this PR.
Go to "Actions"->"Benchmark a pull request"->[the most recent run]->"Artifacts" (at the bottom).

[codecov]

Codecov Report

Attention: Patch coverage is 55.55556% with 4 lines in your changes missing coverage. Please review.

Project coverage is 85.96%. Comparing base (d1ca027) to head (ba54d7c).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/multivariate/optimize/optimize.jl	50.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1155      +/-   ##
==========================================
+ Coverage   85.90%   85.96%   +0.05%     
==========================================
  Files          46       46              
  Lines        3584     3584              
==========================================
+ Hits         3079     3081       +2     
+ Misses        505      503       -2     

☔ 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.