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/seal_input_once.wat

@@ -0,0 +1,22 @@
+;; Stores a value of the passed size. The host function is called once.
+(module
+	(import "seal0" "seal_input" (func $seal_input (param i32 i32)))
+	(import "env" "memory" (memory 1 1))
+
+	;; [0, 8) buffer to write input
+
+	;; [8, 12) size of the input buffer
+	(data (i32.const 8) "\04")
+
+	(func (export "call")
+		;; instructions to consume engine fuel
+		(drop
+			(i32.const 42)
+		 )
+
+ 	    (call $seal_input (i32.const 0) (i32.const 8))
+
+	 )
+
+	(func (export "deploy"))
+)