Renaming: Ribbon -> Band, Interval -> Range

[mwaskom]

• Band is more consistent with err_style="band" in the existing lineplot and is shorter
• Range is more about brevity than consistency, but Interval could be useful as a stat in the future. I went back and forth on this one a lot, Span could also work but I think that will be held in reserve for a bar-type interval mark. FWIW Range is consistent with geom_pointrange/geom_linerange.

[codecov]

Codecov Report

Merging #2945 (4438bb4) into master (a1ede5e) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #2945   +/-   ##
=======================================
  Coverage   98.30%   98.30%           
=======================================
  Files          69       69           
  Lines       22996    22996           
=======================================
  Hits        22607    22607           
  Misses        389      389           

Impacted Files	Coverage Δ
seaborn/_marks/area.py	96.25% <100.00%> (ø)
seaborn/_marks/line.py	100.00% <100.00%> (ø)
seaborn/objects.py	100.00% <100.00%> (ø)
tests/_marks/test_area.py	100.00% <100.00%> (ø)
tests/_marks/test_line.py	100.00% <100.00%> (ø)