Extend EndianNat to convert from nat #7771

Job	Run time
test-and-release-macos	18m 2s
test-and-release-macos (no-std)	3m 40s
fmt	1m 3s
test-and-release-macos (no-alloc)	3m 52s
smoke-test-and-release-macos-x86	17m 29s
test-and-release-macos (record-history)	3m 58s
test-and-release-macos (cvc5)	2m 57s
smoke-test-and-release-windows	8m 26s
test-and-release-macos (singular)	5m 3s
smoke-test-and-release-linux	7m 51s
release	0s
	1h 12m 21s

Provide feedback