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/store_call.wat

@@ -0,0 +1,45 @@
+;; Stores a value of the passed size.
+(module
+	(import "seal0" "seal_set_storage" (func $seal_set_storage (param i32 i32 i32)))
+	(import "seal0" "seal_input" (func $seal_input (param i32 i32)))
+	(import "env" "memory" (memory 16 16))
+
+	;; [0, 32) storage key
+	(data (i32.const 0) "\01")
+
+	;; [32, 36) buffer where input is copied (expected size of storage item)
+
+	;; [36, 40) size of the input buffer
+	(data (i32.const 36) "\04")
+
+	(func $assert (param i32)
+		(block $ok
+			(br_if $ok
+				(get_local 0)
+			)
+			(unreachable)
+		)
+	)
+
+	(func (export "call")
+		(call $seal_input (i32.const 32) (i32.const 36))
+
+		;; assert input size == 4
+		(call $assert
+			(i32.eq
+				(i32.load (i32.const 36))
+				(i32.const 4)
+			)
+		)
+
+		;; place a value in storage, the size of which is specified by the call input.
+		;; we don't care about the contents of the storage item
+		(call $seal_set_storage
+			(i32.const 0)		;; Pointer to storage key
+			(i32.const 0)		;; Pointer to value
+			(i32.load (i32.const 32))	;; Size of value
+		)
+	)
+
+	(func (export "deploy"))
+)