selftest: tcp: Define the reverse order bind() tests explicitly.

Currently, bind_wildcard.c calls bind() twice for two addresses and
checks the pre-defined errno against the 2nd call.  Also, the two
bind() calls are swapped to cover various patterns how bind buckets
are created.

However, only testing two addresses is insufficient to detect regression.
So, we will add more bind() calls, and then, we need to define different
errno for each bind() per test case.

As a prepartion, let's define the reverse order bind() test cases as
fixtures.

No functional changes are intended.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20240326204251.51301-5-kuniyu@amazon.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>