For a column of type `frozen<list<T>>` in base table, a corresponding
column of type `frozen<map<timeuuid, T>>` is created in cdc log.
Although a similar change of type takes place in case of non-frozen
lists, this is unneeded in case of frozen lists - frozen collections are
atomic, therefore there is no need for complicated type that will be
able to represent a column update that depends on its previous value
(e.g. appending elements to the end of the list).
Moreover, only cdc log table creation logic performs this type change
for frozen lists. The logic of `transformer::transform`, which is
responsible for creation of mutations to cdc log, assumes that atomic
columns will have their types unchanged in cdc log table. It simply
copies new value of the column from original mutation to the cdc log
mutation. A serialized frozen list might be copied to a field that is of
frozen map type, which may cause the field to become impossible to
deserialize.
This patch causes frozen list base table columns to have a corresponding
column in cdc log with the same type.
A test is added which asserts that the type of cdc log columns is not
changed in the case of frozen base columns.
Tests: unit(dev)
Fixes#6172
ff80b7c3e2