[c++/python] Switch to std::span

[XanthosXanthopoulos]

Continuing the migration to C++20, this PR replaces tcb::span with std::span

Context: #3154 [sc-57301]

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.63%. Comparing base (f5a3dbc) to head (5d9dfff).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3340      +/-   ##
==========================================
+ Coverage   85.53%   85.63%   +0.10%     
==========================================
  Files          54       54              
  Lines        5703     5703              
==========================================
+ Hits         4878     4884       +6     
+ Misses        825      819       -6     

Flag	Coverage Δ
python	85.63% <ø> (+0.10%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
python_api	85.63% <ø> (+0.10%)	⬆️
libtiledbsoma	∅ <ø> (∅)

---- 🚨 Try these New Features:

• Flaky Tests Detection - Detect and resolve failed and flaky tests

[johnkerl]

@XanthosXanthopoulos I know you still have this as draft, but, since CI is green, and with respect for timezone skew I've gone ahead and approved it so it'll be ready for you to merge in your morning.

Thanks for doing this! :)