Reversing the whole range_tombstone_list
into reversed_range_tombstones is inefficient
and can lead to reactor stalls with a large number of
range tombstones.
Instead, iterate over the range_tombsotne_list in reverse
direction and reverse each range_tombstone as we go,
keeping the result in the optional cookie.reversed_rt member.
While at it, this series contains some other cleanups on this path
to improve the code readability and maybe make the compiler's life
easier as for optimizing the cleaned-up code.
Closes#11271
* github.com:scylladb/scylladb:
mutation: consume_clustering_fragments: get rid of reversed_range_tombstones;
mutation: consume_clustering_fragments: reindent
mutation: consume_clustering_fragments: shuffle emit_rt logic around
mutation: consume, consume_gently: simplify partition_start logic
mutation: consume_clustering_fragments: pass iterators to mutation_consume_cookie ctor
mutation: consume_clustering_fragments: keep the reversed schema in cookie
mutation: clustering_iterators: get rid of current_rt
mutation_test: test_mutation_consume_position_monotonicity: test also consume_gently
0e5b86d3da