Refactor and update packetbeat DHCP parsers

[fearful-symmetry]

Proposed commit message

This is a rather large PR that completely updates the DHCPv4 parser for a number of reasons:

1. Numerous portions of the code did not properly handle malformed data, making it easy to craft packets that could crash packetbeat
2. A lot of the above-mentioned buggy code came from custom logic rendered obsolete by newer versions of the DHCP parsing library we were using.
3. Our code did not conform to the DHCPv4 spec; some options, such as router allow for multiple address fields, although we only parsed the first field.

Putting this in draft, as there's portions of the code I need to clean up, and I would like to add more tests.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works. Where relevant, I have used the stresstest.sh script to run them under stress conditions and race detector to verify their stability.
• I have added an entry in ./changelog/fragments using the changelog tool.

Disruptive User Impact

The router field now returns a list, and not a single address. Returning a single address is technically not in spec, and was a bug.

[github-actions]

🤖 GitHub comments

Just comment with:

• run docs-build : Re-trigger the docs validation. (use unformatted text in the comment!)

[mergify]

This pull request does not have a backport label.
If this is a bug or security fix, could you label this PR @fearful-symmetry? 🙏.
For such, you'll need to label your PR with:

• The upcoming major version of the Elastic Stack
• The upcoming minor version of the Elastic Stack (if you're not pushing a breaking change)

To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit
• backport-active-all is the label that automatically backports to all active branches.
• backport-active-8 is the label that automatically backports to all active minor branches for the 8 major.
• backport-active-9 is the label that automatically backports to all active minor branches for the 9 major.

[elasticmachine]

Pinging @elastic/sec-linux-platform (Team:Security-Linux Platform)

[cmacknz]

Approving go.mod changes.

[github-actions]

@Mergifyio backport 8.19 9.2 9.3

[mergify]

backport 8.19 9.2 9.3

✅ Backports have been created

Details

• #48735 [8.19](backport #48414) Refactor and update packetbeat DHCP parsers has been created for branch 8.19 but encountered conflicts

Cherry-pick of a64fa45 has failed:

On branch mergify/bp/8.19/pr-48414
Your branch is up to date with 'origin/8.19'.

You are currently cherry-picking commit a64fa457c.
  (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:   NOTICE.txt
	new file:   changelog/fragments/1768328474-refactor-dhcpv4-fix-parsing-bugs.yaml
	modified:   packetbeat/decoder/decoder.go
	modified:   packetbeat/protos/dhcpv4/dhcpv4.go
	modified:   packetbeat/protos/dhcpv4/dhcpv4_test.go
	deleted:    packetbeat/protos/dhcpv4/option_ip_address.go
	deleted:    packetbeat/protos/dhcpv4/option_ip_addresses.go
	deleted:    packetbeat/protos/dhcpv4/option_text.go
	modified:   packetbeat/protos/dhcpv4/options.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   go.mod
	both modified:   go.sum

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

• #48736 [9.2](backport #48414) Refactor and update packetbeat DHCP parsers has been created for branch 9.2
• #48737 [9.3](backport #48414) Refactor and update packetbeat DHCP parsers has been created for branch 9.3