alternator-test: rewrite ListTables test
alternator-test: rewrite ListTables test

In our tests, we cannot really assume that ListTables should returns *only*
the tables we created for the test, or even that a page size of 100 will
be enough to list our 3 pages. The issue is that on a shared DynamoDB, or
in hypothetical cases where multiple tests are run in parallel, or previous
tests had catestrophic errors and failed to clean up, we have no idea how
many unrelated tables there are in the system. There may be hundreds of
them.  So every ListTables test will need to use paging.

So in this re-implementation, we begin with a list_tables() utility function
which calls ListTables multiple times to fetch all tables, and return the
resulting list (we assume this list isn't so huge it becomes unreasonable
to hold it in memory). We then use this utility function to fetch the table
list with various page sizes, and check that the test tables we created are
listed in the resulting list.

There's no longer a separate test for "all" tables (really was a page of 100
tables) and smaller pages (1,2,3,4) - we now have just one test that does the
page sizes 1,2,3,4, 50 and 100.

Signed-off-by: Nadav Har'El <625169824b719df98706d88646d0aae6f368ae4d@scylladb.com>

avikivity/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla