[META] Kubernetes version upgrade

[marcelovilla]

With k8s 1.26 unavailable in DigitalOcean and coming to the end of standard support in AWS, GCP and Azure, users should start upgrading their k8s versions.

There is already #2276 to update the highest k8s supported version in Nebari. That should fix #2285.

Here is a list of k8s versions supported by each cloud provider (might vary depending on regions):

GCP

$ gcloud container get-server-config --region us-central1
Fetching server config for us-central1
channels:
- channel: RAPID
  defaultVersion: 1.29.0-gke.1381000
  validVersions:
  - 1.29.2-gke.1060000
  - 1.29.1-gke.1589000
  - 1.29.0-gke.1381000
  - 1.28.7-gke.1026000
  - 1.28.6-gke.1456000
  - 1.28.3-gke.1286000
  - 1.27.11-gke.1062000
  - 1.27.11-gke.1018000
  - 1.26.14-gke.1044000
  - 1.26.14-gke.1006000
  - 1.25.16-gke.1570000
  - 1.25.16-gke.1537000
- channel: REGULAR
  defaultVersion: 1.27.8-gke.1067004
  validVersions:
  - 1.29.0-gke.1381000
  - 1.28.5-gke.1217000
  - 1.28.3-gke.1286000
  - 1.27.10-gke.1055000
  - 1.27.9-gke.1092000
  - 1.27.8-gke.1067004
  - 1.26.13-gke.1144000
  - 1.26.13-gke.1052000
  - 1.26.8-gke.200
  - 1.25.16-gke.1460000
  - 1.25.16-gke.1360000
- channel: STABLE
  defaultVersion: 1.27.8-gke.1067004
  validVersions:
  - 1.28.3-gke.1286000
  - 1.28.3-gke.1203001
  - 1.28.3-gke.1118000
  - 1.27.8-gke.1067004
  - 1.27.7-gke.1121002
  - 1.26.11-gke.1055000
  - 1.26.10-gke.1101000
  - 1.26.8-gke.200
  - 1.25.16-gke.1041000
  - 1.25.15-gke.1115000
defaultClusterVersion: 1.27.8-gke.1067004

DO

$ doctl kubernetes options versions
Slug            Kubernetes Version    Supported Features
1.29.1-do.0     1.29.1                cluster-autoscaler, docr-integration, ha-control-plane, token-authentication
1.28.6-do.0     1.28.6                cluster-autoscaler, docr-integration, ha-control-plane, token-authentication
1.27.10-do.0    1.27.10               cluster-autoscaler, docr-integration, ha-control-plane, token-authentication

[Adam-D-Lewis]

Seems like this is done since k8s 1.29 is supported now