feat(pageserver): log lease request (#10832)

## Problem

To investigate https://github.com/neondatabase/cloud/issues/23650

## Summary of changes

We log lease requests to see why there are clients accessing things
below gc_cutoff.

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

pageserver/src/page_service.rs

@@ -1799,6 +1799,13 @@ impl PageServerHandler {
                 .as_millis()
                 .to_string()
         });
+
+        info!(
+            "acquired lease for {} until {}",
+            lsn,
+            valid_until_str.as_deref().unwrap_or("<unknown>")
+        );
+
         let bytes = valid_until_str.as_ref().map(|x| x.as_bytes());
 
         pgb.write_message_noflush(&BeMessage::RowDescription(&[RowDescriptor::text_col(