Use flagext module from grafana/dskit

[56quarters]

What this PR does:

This removes pkg/util/flagext and starts making use of the code
from dskit. This is mostly a mechanical change with a few exceptions

• Some extra configuration is now included anywhere we instantiate
  a weaveworks/common server due to upstream changes (this mostly
  happens in tests).
• Lints for using util_log had to be disabled in some places so that
  deprecated CLI flags could be registered (which now requires a
  logger).

Notes to reviewer:

Vendor updates are in a separate commit to hopefully make review a bit easier.

Checklist

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

[pracucci]

Thanks for working on this! I left a couple of comments and then LGTM.

Side node: I'm a bit concerned that to just update dskit we've to update a bunch of dependencies. This may introduce slowdowns when reviewing changes. For this time, I did my best to review all dependencies, but we should have a conversation to find a better workflow here.

The following dep upgrade LGTM:

• github.com/hashicorp/consul/api from v1.8.1 to v1.9.1: checked the "api" changes in the CHANGELOG and haven't seen any breaking change (only improvements and fixes)
• github.com/golang/snappy from v0.0.3 to v0.0.4. A couple of changes:
  • Add ReadByte method, satisfies the io.ByteReader interface golang/snappy#51
  • Fix wrong arm64 scaled register format golang/snappy#61
• github.com/gorilla/mux from v1.7.3 to v1.8.0: checked the release notes, should be good to us
• github.com/spf13/afero from v1.2.2 to v1.3.4: checked the release notes and haven't seen any breaking changes
• github.com/gogo/status from v1.0.3 to v1.1.0: checked the release notes and only Go modules support was introduced
• github.com/grpc-ecosystem/go-grpc-middleware from v1.2.2to v1.3.0: checked the diff mentioned in release notes and I don't see any breaking change
• github.com/weaveworks/common from v0.0.0-20210419092856-009d1eebd624 to v0.0.0-20210722103813-e649eff5ab4a: added HTTPListenNetwork and GRPCListenNetwork, which looks correctly handled in this PR
• go.etcd.io/bbolt from v1.3.5 to v1.3.6: according to release notes just a fix
• google.golang.org/api from v0.48.0 to v0.50.0: according to release notes, it just regenerated regenerate discovery clients
• go.etcd.io/etcd/server/v3 from v3.5.0-alpha.0.0.20210225194612-fa82d11a958a to v3.5.0: moving to stale version, LGTM
• github.com/thanos-io/thanos from v0.19.1-0.20210729154440-aa148f8fdb28 to v0.22.0: few minor changes to code paths not even used by Cortex

[pracucci]

I suggest to pin 1.38.0 with this comment:

// TODO review the change introduced by https://github.com/grpc/grpc-go/pull/4416 before upgrading to 1.39.0
replace google.golang.org/grpc => google.golang.org/grpc v1.38.0

[pracucci]

This is a breaking change to annotate in the CHANGELOG.

[pstibrany]

Cortex changes look good.

[56quarters]

Thanks for the review! I'll try to find a way to not include so many dependency updates in the future.

[pracucci]

Thanks for the review! I'll try to find a way to not include so many dependency updates in the future.

Not your fault! I think we should get better at how we specify dependencies in dskit. Let's continue the conversation offline.

[bboreham]

github.com/weaveworks/common added HTTPListenNetwork and GRPCListenNetwork

The options are -server.http-listen-network and -server.grpc-listen-network, and they allow you to specify tcp4 or tcp6 (or default tcp which is both). weaveworks/common#217