avoid using "is_prime_field" in dynamics #16287

Job	Run time
test-new	15m 5s
test-new	15m 5s
test-mod (sagemath_categories-check)	8m 20s
test-mod (sagemath_categories-check)	8m 20s
test-long (src/sage/[a-f]*)	34m 13s
test-long (src/sage/[a-f]*)	34m 13s
test-long (src/sage/[g-o]*)	36m 38s
test-long (src/sage/[g-o]*)	36m 38s
test-long (src/sage/[p-z]*)	46m 57s
test-long (src/sage/[p-z]*)	46m 33s
test-long (src/doc src/sage_docbuild src/sage_setup)	12m 49s
test-long (src/doc src/sage_docbuild src/sage_setup)	12m 49s
coverage-report	18m 55s
coverage-report	20m 50s
	5h 47m 25s

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