Upgrade Thanos and its dependencies

[pracucci]

What this PR does

In this PR I'm upgrading Thanos and some dependencies coming with it. Thanos changes are minimal, but include a couple of fixes we want:

• Fix miekgdns resolver to work with CNAME records too thanos-io/thanos#5271 from me to fix memcached dns+ addresses resolve from CNAME #1654
• Change error cleanup in objstore.DownloadDir to delete files not destination dir thanos-io/thanos#5229 from @dimitarvdimitrov

I checked the other upgraded dependencies, and LGTM:

• github.com/prometheus/client_golang from v1.11.0 to v1.12.1: checked the release notes, added support for go 1.17 metrics collector and TSDB API, some enhancements
• google.golang.org/grpc from v1.41.1 to v1.43.0: checked the release notes, API and behaviour changes shouldn't affect us
• github.com/felixge/httpsnoop from v1.0.1 to v1.0.2: checked the diff and changes look safe to me. The removal of the mutex in this PR makes sense to me
• github.com/aws/aws-sdk-go from v1.42.28 to v1.42.31: checked the diff, just added new endpoints

Which issue(s) this PR fixes or relates to

Fixes #1654

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[aknuds1]

Linting fails, AFAICT due to gRPC upgrade.

[pracucci]

Linting fails, AFAICT due to gRPC upgrade.

Right. I've replaced grpc.WithInsecure() (now deprecated) with grpc.WithTransportCredentials(insecure.NewCredentials()). Under the hood they're the exact same.

[aknuds1]

LGTM

[dimitarvdimitrov]

LGTM