[c++] Match zero-basing for old/new sparse-array shapes

[johnkerl]

Issue and/or context: As pointed out by @XanthosXanthopoulos .

Changes:

This makes the zero-basing logic the same for both old-style and new-style (pre-1.15 and post-1.15) sparse arrays the same.

It also renames some methods which had names that did not well reflect their purposes.

No unit tests are changed, so all passes still: this mod is a no-op for all non-spatial data since those all have soma domain/maxdomain (core current domain/domain) starting at 0. However, this helps clear the path for further development on other arrays which may have their domain/maxdomain not starting at zero.

Notes for Reviewer:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.27%. Comparing base (e8ef0ac) to head (38ba1c4).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3439      +/-   ##
==========================================
+ Coverage   86.22%   86.27%   +0.04%     
==========================================
  Files          55       55              
  Lines        6295     6295              
==========================================
+ Hits         5428     5431       +3     
+ Misses        867      864       -3     

Flag	Coverage Δ
python	86.27% <ø> (+0.04%)	⬆️

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

Components	Coverage Δ
python_api	86.27% <ø> (+0.04%)	⬆️
libtiledbsoma	∅ <ø> (∅)