With higher values of 'calc-string-maximum-character', rules
made up of glyphs of non-unit width can be the wrong length.
Calculate the number of characters in the rule based on the
display width, rounded up to the nearest integer. Refines
feature introduced in bug#78528.
* lisp/calc/calccomp.el (math-comp-simplify-term): Calculate
rule width with a ratio of 'string-pixel-width's.