feat: initial snmp support

[jajeffries]

Adds snmp based discovery to orb agent. See netboxlabs/orb-discovery#68 for details.

Note: This PR requires the orb discovery PR to be merged first so that the snmp-discovery docker image can be pushed.

[github-actions]

Go test coverage

STATUS	ELAPSED	PACKAGE	COVER	PASS	FAIL	SKIP
🟢 PASS	1.02s	github.com/netboxlabs/orb-agent/agent	0.0%	1	0	0
🟢 PASS	0.01s	github.com/netboxlabs/orb-agent/agent/backend	0.0%	0	0	0
🟢 PASS	4.03s	github.com/netboxlabs/orb-agent/agent/backend/devicediscovery	77.7%	2	0	0
🟢 PASS	0.00s	github.com/netboxlabs/orb-agent/agent/backend/mocks	0.0%	0	0	0
🟢 PASS	4.02s	github.com/netboxlabs/orb-agent/agent/backend/networkdiscovery	77.5%	2	0	0
🟢 PASS	4.02s	github.com/netboxlabs/orb-agent/agent/backend/otel	76.4%	2	0	0
🟢 PASS	3.02s	github.com/netboxlabs/orb-agent/agent/backend/pktvisor	67.8%	2	0	0
🟢 PASS	4.03s	github.com/netboxlabs/orb-agent/agent/backend/snmpdiscovery	77.5%	2	0	0
🟢 PASS	4.03s	github.com/netboxlabs/orb-agent/agent/backend/worker	76.9%	2	0	0
🟢 PASS	1.05s	github.com/netboxlabs/orb-agent/agent/configmgr	47.9%	9	0	0
🟢 PASS	1.01s	github.com/netboxlabs/orb-agent/agent/policies	100.0%	15	0	0
🟢 PASS	1.03s	github.com/netboxlabs/orb-agent/agent/policymgr	70.3%	10	0	0
🟢 PASS	2.51s	github.com/netboxlabs/orb-agent/agent/secretsmgr	51.8%	45	0	0
🟢 PASS	1.01s	github.com/netboxlabs/orb-agent/agent/version	100.0%	1	0	0

Total coverage: 61.9%

[Copilot]

Copilot reviewed 4 out of 7 changed files in this pull request and generated no comments.

Files not reviewed (3)

• Makefile: Language not supported
• agent/docker/Dockerfile: Language not supported
• go.mod: Language not supported