Support gauge/counter distinction in Linux observer (#1242) #4099

Job	Run time
cargo-deny	33s
Test Suite	32m 15s
Rust Actions (Check/Fmt/Clippy) (ubuntu-latest)	54s
Rust Actions (Check/Fmt/Clippy) (macos-latest)	1m 11s
actionlint	4s
action-sha-pin-check	37s
buf	9s
Integration Tests	4m 31s
Kani Proofs (lading_throttle)	1m 45s
Loom Proofs (lading_signal)	5m 48s
Kani Proofs (lading_payload)	1m 18s
	49m 5s

Provide feedback