I keep forgetting that primitive types are NOT initialized during construction. :|

See a85641446c30247c4e948263f0f8c1147ed4efb9

Disable copy/assign on them, as they shouldn't.

Make constructor / destructor call init_shallow/fini_shallow,
and make those idempotent.  So, these three can be constructed
on stack now and no init/fini call is needed.  As such,
hb_auto_t<> is not needed anymore.  I'll remove that separately.

It was arbitrary that this struct had it and not dozens of others.

Older C++ doesn't allow struct-with-constructor in union.

Newer compilers / language allows structs with constructor in union.
So, this was not actually testing anything.  Indeed, the recent
change in DISALLOW_COPY *is* making some of our types non-POD.
That broke some bots.

Just remove this since it wasn't doing much, and I'd rather have
DISALLOW_COPY.

Finally!  Catches hard-to-find errors like this:

-    const SortedArrayOf<SVGDocumentIndexEntry> docs = this+svgDocEntries;
+    const SortedArrayOf<SVGDocumentIndexEntry> &docs = this+svgDocEntries;

We implement this for our array types.  This, in turn, trickles down
into all types that embed the arrays.  So, as long as we define all
open-ended structs in terms of Array types (all can be done using
UnsizedArrayOf), this achieves the goal of making uncopyable all
structs that are variable-sized.  Yay!

Revive and rename dump-emoji to test-ot-color but use public APIs instead