Rework static memory segment creation; Fix stdlib gc hooks not marking own fields; Align everything to 8 bytes that might be touched by GC

tests/compiler/std/gc-array.ts

@@ -0,0 +1,23 @@
+import "allocator/arena";
+import "collector/itcm";
+
+class Foo {
+}
+
+var arr: Foo[] = [];
+
+gc.collect(); // should do nothing
+
+arr[0] = {};
+
+gc.collect(); // should do nothing
+
+arr[1] = {};
+
+gc.collect(); // should do nothing
+
+arr[0] = {};
+
+gc.collect(); // should collect the old one
+
+export function main(): i32 { return 0; }