Merge branch 'ps/reftable-binsearch-updates'

Reftable code clean-up and some bugfixes. * ps/reftable-binsearch-updates: reftable/block: avoid decoding keys when searching restart points reftable/record: extract function to decode key lengths reftable/block: fix error handling when searching restart points reftable/block: refactor binary search over restart points reftable/refname: refactor binary search over refnames reftable/basics: improve `binsearch()` test reftable/basics: fix return type of `binsearch()` to be `size_t`