Add model for vstd Set and prove its axioms #6490

Job	Run time
fmt	1m 32s
test-and-release-macos	12m 15s
smoke-test-and-release-linux	6m 21s
smoke-test-and-release-macos-x86	9m 39s
test-and-release-macos (record-history)	3m 12s
test-and-release-macos (no-std)	2m 26s
smoke-test-and-release-windows	8m 19s
test-and-release-macos (no-alloc)	2m 55s
test-and-release-macos (singular)	3m 38s
test-and-release-macos (cvc5)	3m 12s
release	0s
	53m 29s

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