[9.3](backport #46793) Bump Go version to 1.25.8

[mergify]

This PR bumps up the Golang version to 1.25.8. It also:

• removes the ms_tls13kdf Golang build tag when building in FIPS mode because this tag was only needed with Golang versions 1.24.x.
• sets ths GODEBUG=tlsmlkem=0 environment variable when running FIPS140-only unit tests. This prevents errors like so: Failed to connect: crypto/ecdh: use of X25519 is not allowed in FIPS 140-only mode.
• replaces any fmt.Sprintf("%s:%d", ip, port) code fragments with net.JoinHostPort(ip, strconv.Itoa(int(port))) to work with the new hostport go vet analyzer.

  ---

  This is an automatic backport of pull request Bump Go version to 1.25.8 #46793 done by Mergify.

[mergify]

Cherry-pick of c1cb121 has failed:

On branch mergify/bp/9.3/pr-46793
Your branch is up to date with 'origin/9.3'.

You are currently cherry-picking commit c1cb121b7.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   .github/workflows/golangci-lint.yml
	modified:   .go-version
	modified:   NOTICE.txt
	modified:   auditbeat/Dockerfile
	new file:   changelog/fragments/1760385532-bump-golang-1.25.8.yaml
	modified:   dev-tools/kubernetes/filebeat/Dockerfile.debug
	modified:   dev-tools/kubernetes/heartbeat/Dockerfile.debug
	modified:   dev-tools/kubernetes/metricbeat/Dockerfile.debug
	modified:   dev-tools/mage/fips-settings.yaml
	modified:   dev-tools/mage/gotest.go
	modified:   dev-tools/packaging/package_test.go
	modified:   filebeat/magefile.go
	modified:   go.mod
	modified:   heartbeat/Dockerfile
	modified:   heartbeat/hbtest/hbtestutil.go
	modified:   heartbeat/monitors/active/http/http_test.go
	modified:   libbeat/processors/add_kubernetes_metadata/indexers.go
	modified:   libbeat/processors/add_kubernetes_metadata/indexers_test.go
	modified:   metricbeat/Dockerfile
	modified:   metricbeat/helper/server/tcp/tcp_test.go
	modified:   metricbeat/helper/server/udp/udp_test.go
	modified:   metricbeat/magefile.go
	modified:   metricbeat/module/apache/status/status_test.go
	modified:   metricbeat/module/http/_meta/Dockerfile
	modified:   metricbeat/module/vsphere/_meta/Dockerfile
	modified:   packetbeat/Dockerfile
	modified:   testing/go-ech/ech.go
	modified:   x-pack/metricbeat/magefile.go
	modified:   x-pack/metricbeat/module/airflow/statsd/data_test.go
	modified:   x-pack/metricbeat/module/stan/_meta/Dockerfile
	modified:   x-pack/packetbeat/scripts/mage/pcap.go
	modified:   x-pack/packetbeat/tests/system/app_test.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   go.sum
	both modified:   libbeat/docs/version.asciidoc

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[github-actions]

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