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.

src/api.js

@@ -16,7 +16,7 @@ async function call(method, path, data) {
 }
 
 export default {
-	status: () => call('get', '/status'),
+	status: (allRuns = false) => call('get', '/status', allRuns ? { allRuns: true } : undefined),
 	initKey: (passphrase, deleteDelayDays, label) => call('post', '/key', { passphrase, deleteDelayDays, label }),
 	addSlot: (passphrase, label) => call('post', '/key/slots', { passphrase, label }),
 	replaceSlot: (slot, passphrase, label) => call('put', `/key/slots/${slot}`, { passphrase, label }),