Merge branch 'jk/chunk-bounds'

Merge branch 'jk/chunk-bounds'

The codepaths that read "chunk" formatted files have been corrected
to pay attention to the chunk size and notice broken files.

* jk/chunk-bounds: (21 commits)
  t5319: make corrupted large-offset test more robust
  chunk-format: drop pair_chunk_unsafe()
  commit-graph: detect out-of-order BIDX offsets
  commit-graph: check bounds when accessing BIDX chunk
  commit-graph: check bounds when accessing BDAT chunk
  commit-graph: bounds-check generation overflow chunk
  commit-graph: check size of generations chunk
  commit-graph: bounds-check base graphs chunk
  commit-graph: detect out-of-bounds extra-edges pointers
  commit-graph: check size of commit data chunk
  midx: check size of revindex chunk
  midx: bounds-check large offset chunk
  midx: check size of object offset chunk
  midx: enforce chunk alignment on reading
  midx: check size of pack names chunk
  commit-graph: check consistency of fanout table
  midx: check size of oid lookup chunk
  commit-graph: check size of oid fanout chunk
  midx: stop ignoring malformed oid fanout chunk
  t: add library for munging chunk-format files
  ...