feat: COS and COS Lite 3.0

[MichaelThamm]

Issue

Once we have all the charm and Terraform module releases for the components of COS and COS Lite, we can release COS and COS Lite 3.0 for our users.

Solution

This PR prepares a few high-level items:

1. Pin the charm tracks per component to their new workload tracks.
   • The exception are SSC, S3-integrator, and Traefik which do not have these tracks yet
2. All component TF modules are pinned to their respective tags
   • SSC and Traefik are pinned to rev653 and rev301 respectively bc they are externally maintained and we do not have any better tags.
3. The default base is bumped to 26.04
4. Update the cross-track upgrade itests:

flowchart LR

COS-2 --(upgrade/apply)--> COS-3.0 --(upgrade/apply)--> COS

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Checklist

• I have added or updated relevant documentation.
  • docs: COS release notes for breaking changes and features #378
• PR title makes an appropriate release note and follows conventional commits syntax.
• Merge target is the correct branch, and relevant tandem backport PRs opened.
• Add the risk upgrades for the new 3.0 track
• Review this PR to check if there are any changes worth porting in.
  • Also, git diff main track/3.0 to see what needs backporting or to be added to main.

Context

We will not release COS Dev and test cross-track upgrades because we will eventually remove it

For COS Lite:

tracks = {
    alertmanager  = "0.31"
    catalogue     = "3.0"
    grafana       = "12.4"
    loki          = "3.7"
    prometheus   = "3.11"
    ssc           = "1"
    traefik = "latest"
}

and COS:

tracks = {
    alertmanager  = "0.31"
    catalogue     = "3.0"
    grafana       = "12.4"
    loki          = "3.7"
    mimir         = "2.17"
    otelcol       = "0.130"
    s3_integrator = "2"
    ssc           = "1"
    tempo         = "2.10"
    traefik = "latest"
}

Testing Instructions

The solution tests check for cross-track upgrades already.

Upgrade Notes

https://documentation.ubuntu.com/observability/latest/how-to/deploy-and-manage/upgrade/

Our users will have to

[mmkay]

A few smol comments on the referred tags: for catalogue and otelcol-k8s they don't seem to exist (yet?)