Cranelift: Implement iadd_cout on x64 for 32- and 64-bit integers (#5285)

* Split the `iadd_cout` runtests by type

* Implement `iadd_cout` for 32- and 64-bit values on x64

* Delete trailing whitespace in `riscv/lower.isle`

cranelift/filetests/filetests/runtests/iaddcout-i16.clif

@@ -0,0 +1,29 @@
+test interpret
+test run
+target aarch64
+; target s390x
+; target x86_64
+; target riscv64
+
+function %iaddcout_i16_v(i16, i16) -> i16 {
+block0(v0: i16, v1: i16):
+    v2, v3 = iadd_cout v0, v1
+    return v2
+}
+; run: %iaddcout_i16_v(0, 1) == 1
+; run: %iaddcout_i16_v(100, 27) == 127
+; run: %iaddcout_i16_v(100, 28) == 128
+; run: %iaddcout_i16_v(32000, 767) == 32767
+; run: %iaddcout_i16_v(32000, 768) == -32768
+
+function %iaddcout_i16_c(i16, i16) -> i8 {
+block0(v0: i16, v1: i16):
+    v2, v3 = iadd_cout v0, v1
+    return v3
+}
+; run: %iaddcout_i16_c(0, 1) == 0
+; run: %iaddcout_i16_c(100, 27) == 0
+; run: %iaddcout_i16_c(100, 28) == 0
+; run: %iaddcout_i16_c(32000, 767) == 0
+; run: %iaddcout_i16_c(32000, 768) == 1
+