eigrpd: improve validation and error-handling in tlv parsing (backport #21316)

[mergify]

Add more length validation before accessing packet data; add error-detection in several paths; try to skip unknown TLV types in more cases.

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This is an automatic backport of pull request #21316 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 284c966 has failed:

On branch mergify/bp/stable/10.3/pr-21316
Your branch is up to date with 'origin/stable/10.3'.

You are currently cherry-picking commit 284c966d5.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   eigrpd/eigrp_query.c
	modified:   eigrpd/eigrp_reply.c
	modified:   eigrpd/eigrp_siaquery.c
	modified:   eigrpd/eigrp_siareply.c

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   eigrpd/eigrp_packet.c
	both modified:   eigrpd/eigrp_update.c

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[greptile-apps]

Target branch is not in the allowed branches list.

[mjstapp]

looks like auto-backports aren't working; closing