The generator was first setting the marker then applied tombstones.
The marker was set like this:
row.marker() = random_row_marker();
Later, when shadowable tombstones were applied, they were compacted
with the marker as expected.
However, the key for the row was chosen randomly in each iteration and
there are multiple keys set, so there was a possibility of a key clash
with an earlier row. This could override the marker without applying
any tombstones, which is conditional on random choice.
This could generate rows with markers uncompacted with shadowable tombstones.
This broken row_cache_test::test_concurrent_reads_and_eviction on
comparison between expected and read mutations. The latter was
compacted because it went through an extra merge path, which compacts
the row.
Fix by making sure there are no key clashes.
Closes#11663
(cherry picked from commit 5268f0f837)
f878a34da3