feat(lib/backend): add functionality to close clients (#451)

* feat(lib/backend): add functionality to close clients

What?
This PR aims to add functionality to close the clients and it's
resources in case the resources have closers.

Why?
There are use cases in for gcsbacknd using `storage.transfermanager` to
close the single downloader it creates. If we don't close it, there's a
possibility of leaking resources.

How?
Add `Close` to client interface and implement the method for each
client.\
Then `backend.Manager` will use them to expose a `Close()` method that
can be used by build-index and origin to close them.

* add close methods to tests for proper cleanups

* resolved comments

Add eth1 to supported interfaces (#448)

We have a use case for servers with an eth1 interface.

Cache for verification requests (#441)

* Verify cache

* Redundant test

* Comment out only-new-issues:

* Remove push

* Decrease TTL, move to a folder

* Formatting

* push on master

* Benchmarking

* Cache metrics only

* Benchmark step in the pipeline

fix: fix upload step unit_test job (#439)

The upload step of the unit test CI job was failing due to the fact that
the go test commad was not even emitting json. This change aims to fix
that also.

removing unused consts, errors and methods (#436)

fix: upgrade dependencies to fix critical CVEs (#417)

What?
Upgrade `github.com/emicklei/go-restful` and `github.com/gorilla/handlers`

Why?
All the above packages' current versions have critical CVEs:
CVE-2022-1996, CVE-2017-20146 respectively.

How?
Upgrade to the specified fix versions in the CVE bulletins

Reduce number of goroutines in tests that became flaky after Go 1.14 …

…migration (#248)

* Run less go routines in unit tests

* Change number

* Change number

Support for pagination in list catalog (#201)

+ Tagserver now sends list and listRepositories in paginated format
+ TagClient support list and listRepositories with pagination
+ registryoverride support pagination for catalog listing
+ Test cases

Update README.md

Attempt to fix flakey announce test (#112)