Fix: Get the type of Chain.create() from its application (#407)

* Get the type of Chain.create() from its application

* Add test contract

* Update CHANGELOG.md

* Update the tests

* Update tests again

test/contracts/polymorphism_variance_switching_chain_create_fail.aes

@@ -0,0 +1,12 @@
+contract interface I =
+    entrypoint f : () => int
+
+contract C : I =
+    entrypoint f() = 123
+
+main contract Main =
+    stateful entrypoint test() =
+        let c1 : I = Chain.create()       // fails
+        let c2 : C = Chain.create() : I   // fails
+        let c3     = Chain.create() : I   // fails
+        ()