vstd: Add missing cases for lemma2_to64 #6091

Job	Run time
smoke-test-and-release-macos-x86	15m 47s
smoke-test-and-release-windows	8m 2s
fmt	1m 7s
smoke-test-and-release-linux	6m 30s
test-and-release-macos	13m 53s
test-and-release-macos (record-history)	3m 32s
test-and-release-macos (no-std)	4m 1s
test-and-release-macos (no-alloc)	3m 38s
test-and-release-macos (singular)	3m 46s
test-and-release-macos (cvc5)	2m 21s
release	0s
	1h 2m 37s

Provide feedback