Implement bit operations for Cranelift interpreter

Implemented for the Cranelift interpreter:
- `Bitrev` to reverse the order of the bits in an integer.
- `Cls` to count the leading bits which are the same as the sign bit in
an integer, yielding one less than the size of the integer for 0 and -1.
- `Clz` to count the number of leading zeros in the bitwise representation of the
integer.
- `Ctz` to count the number of trailing zeros in the bitwise representation of the
integer.
- `Popcnt` to count the number of ones in the bitwise representation of the
integer.

Copyright (c) 2021, Arm Limited

cranelift/filetests/filetests/runtests/ctz-interpret.clif

@@ -0,0 +1,19 @@
+test interpret
+
+function %ctz_i8(i8) -> i8 {
+block0(v0: i8):
+    v1 = ctz v0
+    return v1
+}
+; run: %ctz_i8(1) == 0
+; run: %ctz_i8(0x40) == 6
+; run: %ctz_i8(-1) == 0
+
+function %ctz_i16(i16) -> i16 {
+block0(v0: i16):
+    v1 = ctz v0
+    return v1
+}
+; run: %ctz_i16(1) == 0
+; run: %ctz_i16(0x4000) == 14
+; run: %ctz_i16(-1) == 0