ospfd: fix sequence number check, avoid truncation ambiguity (backport #21096)

[mergify]

ospfd: reject equal cryptographic sequence numbers
Require strictly increasing OSPF crypt sequence numbers for MD5 and HMAC-SHA
authentication checks to prevent replay of the last accepted packet.


ospfd: use 32-bit LS Update LSA count
Match ospf_ls_upd_list_lsa() count type to the 32-bit on-wire field
to avoid truncation ambiguity and keep parsing semantics consistent
with packet validation.<hr>This is an automatic backport of pull request #21096 done by [Mergify](https://mergify.com).

[greptile-apps]

Target branch is not in the allowed branches list.