fix(pageserver): make repartition error critical (#10872)

## Problem

Read errors during repartition should be a critical error.

## Summary of changes

<del>We only have one call site</del> We have two call sites of
`repartition` where one of them is during the initial image upload
optimization and another is during image layer creation, so I added a
`critical!` here instead of inside `collect_keyspace`.

---------

Signed-off-by: Alex Chi Z <chi@neon.tech>

pageserver/src/http/routes.rs

@@ -2395,6 +2395,7 @@ async fn timeline_checkpoint_handler(
                     match e {
                         CompactionError::ShuttingDown => ApiError::ShuttingDown,
                         CompactionError::Offload(e) => ApiError::InternalServerError(anyhow::anyhow!(e)),
+                        CompactionError::CollectKeySpaceError(e) => ApiError::InternalServerError(anyhow::anyhow!(e)),
                         CompactionError::Other(e) => ApiError::InternalServerError(e)
                     }
                 )?;