Remove `register` macro in Ginac #16230

Job	Run time
test-new	11m 45s
test-mod (sagemath_categories-check)	10m 48s
test-long (src/sage/[a-f]*)	33m 25s
test-long (src/sage/[g-o]*)	43m 8s
test-long (src/sage/[p-z]*)	33m 19s
test-long (src/doc src/sage_docbuild src/sage_setup)	17m 40s
coverage-report	18m 50s
	2h 48m 55s

Provide feedback