Remove use of github.com/pkg/errors

[AlexanderYastrebov]

See pkg/errors#245

We can probably replace it by https://pkg.go.dev/errors#Join introduced in 1.20

[AlexanderYastrebov]

After #2492 we still have it as indirect

$ go mod why -m github.com/pkg/errors
# github.com/pkg/errors
github.com/zalando/skipper/tracing/tracers/jaeger
github.com/uber/jaeger-client-go/config
github.com/pkg/errors

Related to #2153 and #2104

[AlexanderYastrebov]

If jaeger dependency is removed then

$ go mod why -m github.com/pkg/errors
# github.com/pkg/errors
github.com/zalando/skipper/net/redistest
github.com/testcontainers/testcontainers-go
github.com/docker/docker/api/types/registry
github.com/pkg/errors

[AlexanderYastrebov]

There are other dependencies, namely OPA, using github.com/pkg/errors:

$ go mod graph | grep github.com/pkg/errors
github.com/zalando/skipper github.com/pkg/[email protected]
github.com/containerd/[email protected] github.com/pkg/[email protected]
github.com/dgraph-io/badger/[email protected] github.com/pkg/[email protected]
github.com/dgraph-io/[email protected] github.com/pkg/[email protected]
github.com/open-policy-agent/[email protected] github.com/pkg/[email protected]
github.com/open-policy-agent/[email protected] github.com/pkg/[email protected]
github.com/opencontainers/[email protected] github.com/pkg/[email protected]
github.com/testcontainers/[email protected] github.com/pkg/[email protected]