Implemented wide tags for both rbyd commit and lookup

Wide tags are a happy accident that fell out of the realization that we
can view all subtypes of a given tag suptype as a range in our rbyd.
Combining this with how natural it is to operate on ranges in an rbyd
allows us to perform operations on an entire range of subtypes as though
it were a single tag.

- lookup wide tag => find the smallest tag with this tag's suptype, O(log(n))
- remove wide tag => remove all tags with this tag's suptype, O(log(n))
- append wide tag => remove all tags with this tag's suptype, and then
  append our tag, O(log(n))

This is very useful for littlefs, where we've already been using tag's
subtypes to hold extra type info, and have had to rely on awkward
alternatives such as deleting existing subtypes before writing our new
subtype.

For example, when committing file metadata (not yet implemented), we can
append a wide struct tag to update the metadata while also clearing out any
lingering struct tags from previous commits, all in one rbyd append
operation.

This uses another mode bit in-device to change the behavior of
lfsr_rbyd_commit, of which we have a couple:

  vwgrtttt 0TTTTTTT
  ^^^^---^--------^- valid bit (currently unused, maybe errors?)
   '||---|--------|- wide bit, ignores subtype (in-device)
    '|---|--------|- grow bit, don't create new id (in-device)
     '---|--------|- rm bit, remove this tag (in-device)
         '--------|- 4-bit suptype
                  '- leb128 subtype

scripts/dbgmtree.py

@@ -23,6 +23,7 @@ TAG_MROOT       = 0x0304
 TAG_MDIR        = 0x0305
 TAG_MTREE       = 0x0306
 TAG_UATTR       = 0x0400
+TAG_SATTR       = 0x0500
 TAG_ALT         = 0x4000
 TAG_ALTA        = 0x6000
 TAG_CRC         = 0x2000
@@ -157,6 +158,11 @@ def tagrepr(tag, w, size, off=None):
             tag & 0xff,
             ' w%d' % w if w else '',
             size)
+    elif (tag & 0xff00) == TAG_SATTR:
+        return 'sattr 0x%02x%s %d' % (
+            tag & 0xff,
+            ' w%d' % w if w else '',
+            size)
     elif (tag & 0xff00) == TAG_CRC:
         return 'crc%x%s %d' % (
             1 if tag & 0x1 else 0,