Renamed BNAME -> NAME, CCKSUM -> CKSUM

It's probably better to have a separate names for a tag category and any
specific name, but I can't think of a better name for this tag, and I
hadn't noticed that I was already ignoring the C prefix for CCKSUM tags
in many places.

NAME/CKSUM now mean both the specific tag and tag category, which is a
bit of a hack since both happen to be the 0th-subtype of their
categories.

tests/test_btree.toml

@@ -88,7 +88,7 @@ code = '''
                 LFSR_ATTR(bid-(weight_-1)+weight1-1, TAG(tag1), 0, DATA(data1)),
                 (lfsr_data_size(&name) > 0
                     ? LFSR_ATTR(bid-(weight_-1)+weight1,
-                        BNAME, +weight2, DATA(name))
+                        NAME, +weight2, DATA(name))
                     : LFSR_ATTR_NOOP),
                 (lfsr_data_size(&name) > 0
                     ? LFSR_ATTR(bid-(weight_-1)+weight1+weight2-1,