aura/slot_based: Reduce authoring duration of the last produced block (#10154)

This PR adjusts the block authoring to stop producing blocks 1 second
before the scheduled slot change.
This introduces a safety buffer to prevent blocks from being authored
too late for inclusion.

- 2s blocks / 3 cores: The authoring duration of the last block is
reduced from 2s to 1s.
- 500ms blocks / 12 cores: The authoring duration cannot be reduced past
500ms, therefore the last two blocks are no longer authored

### Testing Done

Tested on top of:
- #9880

### 3 cores 2s blocks

```
aura::cumulus: [Parachain] Adjusting authoring duration for slot. authoring_duration=2s duration=1.987s last_reported_slot=Some(Slot(293723040)) next_slot=Slot(293723040) next_duration_change=5.987s next_slot_change=Slot(293723041)
aura::cumulus: [Parachain] Adjusted proposal duration. duration=Some(1.987s)

aura::cumulus: [Parachain] Adjusting authoring duration for slot. authoring_duration=2s duration=1.991s last_reported_slot=Some(Slot(293723040)) next_slot=Slot(293723040) next_duration_change=3.991s next_slot_change=Slot(293723041)
aura::cumulus: [Parachain] Adjusted proposal duration. duration=Some(1.991s)

aura::cumulus: [Parachain] Adjusting authoring duration for slot. authoring_duration=2s duration=1.99s last_reported_slot=Some(Slot(293723040)) next_slot=Slot(293723041) next_duration_change=1.99s next_slot_change=Slot(293723041)
aura::cumulus: [Parachain] Adjusted proposal duration. duration=Some(990ms)
```

### 12 cores 500ms blocks

```
aura::cumulus: [Parachain] Adjusting authoring duration for slot. authoring_duration=2s duration=494ms last_reported_slot=Some(Slot(293724134)) next_slot=Slot(293724134) next_duration_change=1.494s next_slot_change=Slot(293724135) deadline=494ms
aura::cumulus: [Parachain] Adjusted proposal duration. duration=Some(494ms)

aura::cumulus: [Parachain] Adjusting authoring duration for slot. authoring_duration=2s duration=493ms last_reported_slot=Some(Slot(293724134)) next_slot=Slot(293724134) next_duration_change=993ms next_slot_change=Slot(293724135) deadline=0ns
aura::cumulus: [Parachain] Not enough time left in the slot to adjust authoring duration. Skipping block production for the slot. next_duration_change=993ms next_slot_change=Slot(293724135)
aura::cumulus: [Parachain] Adjusted proposal duration. duration=None
aura::cumulus: [Parachain] Not building block due to insufficient authoring duration

aura::cumulus: [Parachain] Adjusting authoring duration for slot. authoring_duration=2s duration=494ms last_reported_slot=Some(Slot(293724136)) next_slot=Slot(293724137) next_duration_change=494ms next_slot_change=Slot(293724137) deadline=0ns
aura::cumulus: [Parachain] Not enough time left in the slot to adjust authoring duration. Skipping block production for the slot. next_duration_change=494ms next_slot_change=Slot(293724137)
aura::cumulus: [Parachain] Adjusted proposal duration. duration=None
aura::cumulus: [Parachain] Not building block due to insufficient authoring duration
```

Part of: #9848

---------

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>
Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: eduardspa <eduard@parity.io>
Co-authored-by: Sebastian Kunert <skunert49@gmail.com>
Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com>

Author: 5 people

cumulus/client/consensus/aura/src/collators/slot_based/block_builder_task.rs

@@ -404,13 +404,26 @@ where
 				validation_data.max_pov_size * 85 / 100
 			} as usize;
 
-			let adjusted_authoring_duration = match slot_timer.time_until_next_slot() {
-				Ok((duration, _slot)) => std::cmp::min(authoring_duration, duration),
-				Err(_) => authoring_duration,
-			};
-
+			let adjusted_authoring_duration =
+				slot_timer.adjust_authoring_duration(authoring_duration);
 			tracing::debug!(target: crate::LOG_TARGET, duration = ?adjusted_authoring_duration, "Adjusted proposal duration.");
 
+			let Some(adjusted_authoring_duration) = adjusted_authoring_duration else {
+				tracing::debug!(
+					target: crate::LOG_TARGET,
+					unincluded_segment_len = parent.depth,
+					relay_parent = ?relay_parent,
+					relay_parent_num = %relay_parent_header.number(),
+					included_hash = ?included_header_hash,
+					included_num = %included_header.number(),
+					parent = ?parent_hash,
+					slot = ?para_slot.slot,
+					"Not building block due to insufficient authoring duration."
+				);
+
+				continue;
+			};
+
 			let Ok(Some(candidate)) = collator
 				.build_block_and_import(
 					&parent_header,