seal: Fail instantiate if new contract is below subsistence threshold (#6719)

* seal: Fail instantiate if new contract is below subsistence threshold

We need each contract that exists to be above the subsistence threshold
in order to keep up the guarantuee that we always leave a tombstone behind
with the exception of a contract that called `ext_terminate`.

* Fixup executor test

* Bump runtime

substrate/bin/node/runtime/src/lib.rs

@@ -105,7 +105,7 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	// and set impl_version to 0. If only runtime
 	// implementation changes and behavior does not, then leave spec_version as
 	// is and increment impl_version.
-	spec_version: 256,
+	spec_version: 257,
 	impl_version: 0,
 	apis: RUNTIME_API_VERSIONS,
 	transaction_version: 1,