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/event_size.wat

@@ -0,0 +1,39 @@
+(module
+	(import "seal0" "seal_deposit_event" (func $seal_deposit_event (param i32 i32 i32 i32)))
+	(import "seal0" "seal_input" (func $seal_input (param i32 i32)))
+	(import "env" "memory" (memory 16 16))
+
+	;; [0, 4) size of the input buffer
+	(data (i32.const 0) "\04")
+
+	(func $assert (param i32)
+		(block $ok
+			(br_if $ok
+				(get_local 0)
+			)
+			(unreachable)
+		)
+	)
+
+	(func (export "call")
+		(call $seal_input (i32.const 4) (i32.const 0))
+
+		;; assert input size == 4
+		(call $assert
+			(i32.eq
+				(i32.load (i32.const 0))
+				(i32.const 4)
+			)
+		)
+
+		;; place a garbage value in storage, the size of which is specified by the call input.
+		(call $seal_deposit_event
+			(i32.const 0) ;; topics_ptr
+			(i32.const 0) ;; topics_len
+			(i32.const 0) ;; data_ptr
+			(i32.load (i32.const 4)) ;; data_len
+		)
+	)
+
+	(func (export "deploy"))
+)