Merge branch 'ps/reftable-hardening' into jch

Merge branch 'ps/reftable-hardening' into jch

The reftable code has been hardened against corrupted tables by
fixing out-of-bounds writes, out-of-bounds reads, and abort calls
during parsing.

* ps/reftable-hardening:
  reftable/table: fix OOB read on truncated table
  reftable/table: fix NULL pointer access when seeking to bogus offsets
  reftable/block: fix OOB read with bogus restart offset
  reftable/block: fix use of uninitialized memory when binsearch fails
  reftable/block: fix OOB read with bogus restart count
  reftable/block: fix OOB read with bogus block size
  reftable/block: fix OOB write with bogus inflated log size
  t/unit-tests: introduce test helper to write reftable blocks
  reftable/record: don't abort when decoding invalid ref value type
  reftable/basics: fix OOB read on binary search of empty range
  oss-fuzz: add fuzzer for parsing reftables
  meson: support building fuzzers with libFuzzer