S3 based recovery (#6155)

Adds a new `time_travel_recover` function to the `RemoteStorage` trait
that allows time travel like functionality for S3 buckets, regardless of
their content (it is not even pageserver related). It takes a different
approach from [this
post](https://aws.amazon.com/blogs/storage/point-in-time-restore-for-amazon-s3-buckets/)
that is more complicated.

It takes as input a prefix a target timestamp, and a limit timestamp:

* executes [`ListObjectVersions`](https://docs.aws.amazon.com/AmazonS3/latest/API/API_ListObjectVersions.html)
* obtains the latest version that comes before the target timestamp
* copies that latest version to the same prefix
* if there is versions newer than the limit timestamp, it doesn't do
anything for the file

The limit timestamp is meant to be some timestamp before the start of
the recovery operation and after any changes that one wants to revert.
For example, it might be the time point after a tenant was detached from
all involved pageservers. The limiting mechanism ensures that the
operation is idempotent and can be retried without causing additional
writes/copies.

The approach fulfills all the requirements laid out in 8233, and is a
recoverable operation. Nothing is deleted permanently, only new entries
added to the version log.

I also enable [nextest retries](https://nexte.st/book/retries.html) to
help with some general S3 flakiness (on top of low level retries).

Part of https://github.com/neondatabase/cloud/issues/8233

.github/workflows/build_and_test.yml

@@ -21,6 +21,7 @@ env:
   COPT: '-Werror'
   AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_DEV }}
   AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_SECRET_KEY_DEV }}
+  NEXTEST_RETRIES: 3
 
 jobs:
   check-permissions: