Introduce `missing-at`/`last-missing` timestamps #6668

Job	Run time
prepare	3s
Check no_std	35s
Build & Test Examples (example_cli)	34s
Build & Test (1.84.0, true, --no-default-features --features miniscript/no-std)	1m 32s
Build & Test Examples (example_bitcoind_rpc_polling)	37s
Check WASM	1m 4s
Build & Test Examples (example_electrum)	54s
Rust clippy	40s
Build & Test (1.84.0, true, --all-features)	1m 17s
Build & Test Examples (example_esplora)	56s
Rust fmt	13s
Build & Test (1.63.0, --no-default-features --features miniscript/no-std)	1m 32s
Build & Test Examples (example_wallet_electrum)	54s
Build & Test (1.63.0, --all-features)	1m 33s
Build & Test Examples (example_wallet_esplora_async)	1m 2s
Build & Test Examples (example_wallet_esplora_blocking)	51s
Build & Test (1.75.0, --no-default-features --features miniscript/no-std)	1m 32s
Build & Test Examples (example_wallet_rpc)	42s
Build & Test (1.75.0, --all-features)	1m 28s
	17m 59s

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