test_range_tombstones_v2 is too strict for this reader -- it expects a
particular sequence of `range_tombstone_change`s, but
multishard_combining_reader, when tested with a small buffer, may
generate -- as expected -- additional (redundant) range tombstone change
pairs (end+start).
Currently we don't observe these redundant fragments due to a bug in
`evictable_reader_v2` but they start appearing once we fix the bug and
the test must be prepared first.
To prepare the test, modify `flat_reader_assertions_v2` so it squashes
redundant range tombstone change pairs. This happens only in non-exact
mode.
Enable exact mode in `test_sstable_reversing_reader_random_schema` for
comparing two readers -- the squashing of `r_t_c`s may introduce an
artificial difference.
5800ce8ddd