Update Istio version to 1.26.4 in the OSSM 3.1.z release.

Sail operator:

• sail operator upstream repo; release-1.0 branch (by https://github.com/istio-ecosystem/sail-operator/pull/1209  )
• sail operator midstream repo; release-3.0 branch (PR is automatically created once ^ will be merged) (by https://github.com/openshift-service-mesh/sail-operator/pull/503 )
  • Finish `istio midstream repo; release-1.24 branch` step before continue!
  • Once ^ will be merge, it is needed to generate helm charts in midstream
    • update `versions.ossm.yaml` file with newer istio values from `versions.yaml`, generate helm charts via `make gen`
      • PR: https://github.com/openshift-service-mesh/sail-operator/pull/506 
    • after that, make sure go.mod is referencing the latest `github.com/openshift-service-mesh/istio` 
      • the job automatically update istio module after istio is merged, see istio section below
    • after that, generate `our packages` in https://github.com/openshift-service-mesh/istio-release;
      • PR: https://github.com/openshift-service-mesh/istio-release/pull/10 
    • after that, update `versions.ossm.yaml` to use our generated charts and regenerate via`make gen`
      • PR: https://github.com/openshift-service-mesh/sail-operator/pull/507 
    • after that (or as part of previous PR), create new "placeholders" images in ossm/values.yaml for new istio version, and update previous version with `shas` of already released images (if there are any from previous istio update )
      • PR:  https://github.com/openshift-service-mesh/sail-operator/pull/507 

Proxy:

• envoy-openssl repo; release/v1.34 branch  (by https://github.com/envoyproxy/envoy-openssl/pull/346 )
• proxy midstream repo; release-1.26 branch (by https://github.com/openshift-service-mesh/proxy/pull/41 )

Ztunnel:

• ztunnel midstream repo; release-1.26 branch  (by https://github.com/openshift-service-mesh/ztunnel/pull/10 )

Istio:

• istio midstream repo; release-1.26 branch, update sha of proxy  (by https://github.com/openshift-service-mesh/istio/pull/486  )
• istio midstream repo; release-1.26 branch, update sha of ztunnel 
  • we don't need this since we use upstream version of ztunnel
• istio midstream repo; release-1.26 branch sync with upstream (by https://github.com/openshift-service-mesh/istio/pull/488 )
  • do not forget to add tide/merge-method-merge label
  • after this, the `update-istio-module` job updates the istio module in sail-operator repo and creates newer PR
    • if no new PR was created, you can run the `go mod edit -replace="istio.io/istio=github.com/openshift-service-mesh/istio@release-1.26";go mod tidy` (for 1.26.z) on sail operator release-3.1 branch and create PR manually, PR : https://github.com/openshift-service-mesh/sail-operator/pull/505 

after that, we need to have new tags which are used in konflux.

• 1.26.4-redhat-rc tag was added to proxy/istio/ztunnel repos

after that when we will have a new build, the jenkins pipelines need to be updated as well: 

• PR: https://gitlab.cee.redhat.com/istio/servicemesh-qe/jenkins-csb-declaration/-/merge_requests/776