use slog for structured logging (#3502)

cmd/dex/config.go

cmd/dex/config_test.go

cmd/dex/serve.go

connector/atlassiancrowd/atlassiancrowd.go

connector/atlassiancrowd/atlassiancrowd_test.go

connector/authproxy/authproxy.go

connector/authproxy/authproxy_test.go

connector/bitbucketcloud/bitbucketcloud.go

connector/gitea/gitea.go

connector/github/github.go

connector/github/github_test.go

connector/gitlab/gitlab.go

connector/google/google.go

connector/google/google_test.go

connector/keystone/keystone.go

connector/ldap/ldap.go

connector/ldap/ldap_test.go

connector/linkedin/linkedin.go

connector/microsoft/microsoft.go

connector/mock/connectortest.go