Merge branch 'ps/reftable-write-options'

The knobs to tweak how reftable files are written have been made available as configuration variables. * ps/reftable-write-options: refs/reftable: allow configuring geometric factor reftable: make the compaction factor configurable refs/reftable: allow disabling writing the object index refs/reftable: allow configuring restart interval reftable: use `uint16_t` to track restart interval refs/reftable: allow configuring block size reftable/dump: support dumping a table's block structure reftable/writer: improve error when passed an invalid block size reftable/writer: drop static variable used to initialize strbuf reftable: pass opts as constant pointer reftable: consistently refer to `reftable_write_options` as `opts`