scripts: csv.py: Replaced -l/--label with -I/-B/-F for hidden fields

It felt weird that adding hidden fields required changing existing
flags unrelated to the field you actually want to affect, and the
upper/lower flag thing seems to work well for -s/-S sooo...

- Replaced -l/--label with -B/--hidden-by for by fields that can
  be hidden from the table renderer.

- Added -F/--hidden-field as a similar thing for field fields.

- Better integrated -i/--enumerate into by fields, now these actually
  maintain related order. And of course added a matching
  -I/--hidden-enumerate flag.

The only downside is this is eating a lot of flag names.. But one of the
nice thing about limiting this complexity to csv.py is it avoids these
flag names cluttering up the other result scripts.

---

The -F/--hidden-fields flag I'm not so sure about, since field exprs
can't really reference each other (single pass). But it does provide
symmetry with -B/--hidden-by, and reserves the name in case hidden field
fields are more useful in the future.

Unfortunately it _is_ annoyingly inconsistent with other hidden fields
(-S/--sort, -D/--define, etc) in that it does end up in output csvs...

But this script is already feeling way over-engineered as is.

scripts/stack.py

@@ -537,14 +537,12 @@ def fold(Result, results, *,
     return folded
 
 def hotify(Result, results, *,
-        enumerate=None,
+        enumerates=None,
         depth=1,
         hot=None,
         **_):
-    # note! hotifying risks confusion if you don't enumerate/have a z
-    # field, since it will allow folding across recursive boundaries
-    import builtins
-    enumerate_, enumerate = enumerate, builtins.enumerate
+    # note! hotifying risks confusion if you don't enumerate/have a
+    # z field, since it will allow folding across recursive boundaries
 
     # hotify only makes sense for recursive results
     assert hasattr(Result, '_children')
@@ -569,8 +567,10 @@ def hotify(Result, results, *,
                         for k, reverse in it.chain(hot, [(None, False)])))
 
             hot_.append(r._replace(**(
-                    ({enumerate_: len(hot_)}
-                            if enumerate_ is not None else {})
+                    # enumerate?
+                    ({e: len(hot_) for e in enumerates}
+                            if enumerates is not None
+                            else {})
                         | {Result._children: []})))
 
             # recurse?