Contracts move fixtures to new crate (#2246)

Small PR that introduce a new crate that will host RISC-V & wasm
fixtures for testing pallet-contracts

substrate/frame/contracts/fixtures/data/debug_message_invalid_utf8.wat

@@ -0,0 +1,28 @@
+;; Emit a debug message with an invalid utf-8 code
+(module
+	(import "seal0" "seal_debug_message" (func $seal_debug_message (param i32 i32) (result i32)))
+	(import "env" "memory" (memory 1 1))
+
+	(data (i32.const 0) "\fc")
+
+	(func $assert_eq (param i32 i32)
+		(block $ok
+			(br_if $ok
+				(i32.eq (get_local 0) (get_local 1))
+			)
+			(unreachable)
+		)
+	)
+
+	(func (export "call")
+		(call $assert_eq
+			 (call $seal_debug_message
+				 (i32.const 0)	;; Pointer to the text buffer
+				 (i32.const 12)	;; The size of the buffer
+			 )
+			 (i32.const 0)	;; Success return code
+		)
+	 )
+
+	(func (export "deploy"))
+)