Fix ImHex pattern tile_size_in_fh truncation and extend tile/AUI/gainmap parsing

[kpchoi]

Updates util/apv.hexpat.

Bug fixes:

• tile_size_in_fh : 32 * NumTiles is truncated to 8 bits by the pattern
  engine whenever 32 * NumTiles >= 256, desynchronizing the whole pattern for
  streams with tile_size_present_in_fh_flag = 1 and NumTiles >= 8. It is now
  an array of 32-bit bitfield members.
• The MSB of the frame_info trailing byte is decoded as use_companding
  (444-16C12 / 4444-16C12, see readme/apv_ext.md) instead of showing
  reserved_zero_8bits = 128, with a warning when set for other profiles.
• Metadata PBUs consume the trailing filler() bytes so subsequent PBUs stay in
  sync, and payload structs consume any unread remainder.
• Guards for undersized metadata payloads (T.35, MDCV, CLL, user-defined),
  malformed pbu_size and tile sizes; invalid tile_info skips the frame data
  with a warning instead of forcing a parse.
• The verbose AU log line now shows the real AU index.

New parsing:

• Frame tiles: per-tile tile_size, tile_header() fields (tile_index,
  tile_data_size[], tile_qp[]) and a sealed tile data blob.
• au_info() (pbu_type 65): num_frames and per-frame pbu_type, group_id,
  frame_info().
• Metadata payload types 20 (ICC profile) and 21 (gainmap), and the gainmap
  frame PBU (pbu_type 28) from the APV gainmap/ICC specification draft.
• profile_idc / chroma_format_idc / pbu_type are shown as enums.

Console output:

• A start line and a summary (AU/PBU/frame/metadata counts, distinct frame
  configurations, metadata payload types).
• Frame info changes are reported with the changed fields at the AU/frame
  position, keyed by (pbu_type, group_id) so coexisting frames such as
  previews are not reported as changes.
• Detailed per-PBU output is available by setting verbose = true at the top
  of the pattern.

[cpncf]

LGTM