pageserver: optionally force image layer creation on timeout (#12529)

This PR introduces a `image_creation_timeout` to page servers so that we
can force the image creation after a certain period. This is set to 1
day on dev/staging for now, and will rollout to production 1/2 weeks
later.

Majority of the PR are boilerplate code to add the new knob. Specific
changes of the PR are:
1. During L0 compaction, check if we should force a compaction if
min(LSN) of all delta layers < force_image_creation LSN.
2. During image creation, check if we should force a compaction if the
image's LSN < force_image_creation LSN and there are newer deltas with
overlapping key ranges.
3. Also tweaked the check image creation interval to make sure we honor
image_creation_timeout.

Vlad's note: This should be a no-op. I added an extra PS config for the
large timeline
threshold to enable this.

---------

Co-authored-by: Chen Luo <chen.luo@databricks.com>

control_plane/src/pageserver.rs

@@ -452,6 +452,12 @@ impl PageServerNode {
                 .map(|x| x.parse::<usize>())
                 .transpose()
                 .context("Failed to parse 'image_creation_threshold' as non zero integer")?,
+            // HADRON
+            image_layer_force_creation_period: settings
+                .remove("image_layer_force_creation_period")
+                .map(humantime::parse_duration)
+                .transpose()
+                .context("Failed to parse 'image_layer_force_creation_period' as duration")?,
             image_layer_creation_check_threshold: settings
                 .remove("image_layer_creation_check_threshold")
                 .map(|x| x.parse::<u8>())