Fast S3 verify and snapshot commit; shorter runs list; durations with days

On S3, index files and the tree segments read back when a snapshot is
written are fetched 16 at a time through the storage's S3 client
(IBackend::getRanges(), getMany()). Blobs that follow each other in a pack
are read as one range on every location. The snapshot is written in a step
of its own and the run shows "commit" meanwhile. On a 1 TB production
repository the check went from about 4 hours to 3.5 minutes.

backup:status and the web interface list the runs of the last 7 days,
running ones and at least the newest 5; --all / "Show older runs" list
all. Durations of a day or more show the days.

psalm-baseline.xml

@@ -218,16 +218,11 @@
     </PropertyNotSetInConstructor>
   </file>
   <file src="lib/Job/BackupRun.php">
-    <ArgumentTypeCoercion>
-      <code><![CDATA[$blobs]]></code>
-    </ArgumentTypeCoercion>
     <MissingParamType>
       <code><![CDATA[$fh]]></code>
     </MissingParamType>
     <PossiblyUndefinedArrayOffset>
       <code><![CDATA[$mtime]]></code>
-      <code><![CDATA[$state['phase']]]></code>
-      <code><![CDATA[$state['stats']]]></code>
     </PossiblyUndefinedArrayOffset>
   </file>
   <file src="lib/Job/ParentCursor.php">