Unify incremental test cases and disable many

The self-hosted aarch64 backend is not currently functional due to the
Liveness changes. A previous commit disabled aarch64 on the behavior
tests; this commit disables it and arm for the test cases. Moreover, all
incremental test cases have been unified into shared cross-platform
cases, which can be gradually enabled as the backends improve.

test/cases/function_pointers.zig

@@ -0,0 +1,30 @@
+const std = @import("std");
+
+const PrintFn = *const fn () void;
+
+pub fn main() void {
+    var printFn: PrintFn = stopSayingThat;
+    var i: u32 = 0;
+    while (i < 4) : (i += 1) printFn();
+
+    printFn = moveEveryZig;
+    printFn();
+}
+
+fn stopSayingThat() void {
+    _ = std.os.write(1, "Hello, my name is Inigo Montoya; you killed my father, prepare to die.\n") catch {};
+}
+
+fn moveEveryZig() void {
+    _ = std.os.write(1, "All your codebase are belong to us\n") catch {};
+}
+
+// run
+// target=x86_64-macos
+//
+// Hello, my name is Inigo Montoya; you killed my father, prepare to die.
+// Hello, my name is Inigo Montoya; you killed my father, prepare to die.
+// Hello, my name is Inigo Montoya; you killed my father, prepare to die.
+// Hello, my name is Inigo Montoya; you killed my father, prepare to die.
+// All your codebase are belong to us
+//