Add tests for uncle timestamps and refactor timestamp type (cherry picked from commitabce09954b) (cherry picked from commitfd512fa12c) Conflicts: core/vm/instructions.go core/vm/jit_test.go
Add tests for uncle timestamps and refactor timestamp type (cherry picked from commitabce09954b) (cherry picked from commitfd512fa12c) Conflicts: core/vm/instructions.go core/vm/jit_test.go