Fix calc number formatting with digit grouping (bug#36689)
The functions math-format-hex and math-format-octal were not implemented, yet called, leading to a crash when using hex or octal radix with digit grouping. * test/lisp/calc/calc-tests.el (calc-test-format-radix): New test. * lisp/calc/calc-ext.el: Don't declare non-existing functions. (math--format-integer-fancy): Don't call non-existing functions. * lisp/calc/calc-bin.el (math-format-binary, math-binary-digits): Simplify, fixing 0-padding bug.