Add support for basic measurement tools

[mattpap]

Very early prototype. The main goals of this PR are the following:

1. Establish a set of "scalar" glyphs (called shapes), that will be useful as basic building blocks of more complex visuals, but without the heaviness of glyphs and legacy cruft of annotations.
2. Establish a more flexible way of specifying coordinates while migrating to use sub-coordinates (e.g. no x_units etc. anymore).

Measurement tools in this PR are a side effect and a practical way of showing those working.

fixes #182

Example:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.63%. Comparing base (69bddb5) to head (276c4d0).
Report is 1 commits behind head on branch-3.5.

❗ Current head 276c4d0 differs from pull request most recent head 9c98436. Consider uploading reports for the commit 9c98436 to get more accurate results

Additional details and impacted files

@@              Coverage Diff               @@
##           branch-3.5   #13279      +/-   ##
==============================================
- Coverage       92.65%   92.63%   -0.02%     
==============================================
  Files             326      323       -3     
  Lines           20736    20640      -96     
==============================================
- Hits            19212    19120      -92     
+ Misses           1524     1520       -4     

[jbednar]

Fixes issue #182, opened ten years ago!!!