Sync up release-line-0.3.21 to state before repo switch

[martinflorian-da]

Fixes DACH-NY/cn-test-failures#4467

CI should tell me if I missed anything important.

To prevent adding something I shouldn't be, I compared with other branches on this repo; a bunch of stuff had to be removed by hand.

Pull Request Checklist

Cluster Testing

• If a cluster test is required, comment /cluster_test on this PR to request it, and ping someone with access to the DA-internal system to approve it.
• If a hard-migration test is required (from the latest release), comment /hdm_test on this PR to request it, and ping someone with access to the DA-internal system to approve it.

PR Guidelines

• Include any change that might be observable by our partners or affect their deployment in the release notes.
• Specify fixed issues with Fixes #n, and mention issues worked on using #n
• Include a screenshot for frontend-related PRs - see README or use your favorite screenshot tool

Merge Guidelines

• Make the git commit message look sensible when squash-merging on GitHub (most likely: just copy your PR description).

[isegall-da]

/hdm_test

[isegall-da]

/hdm_test

[isegall-da]

Ah, testing hdm_test from here was wrong.
Running now:
run-job: deploy-hdm-operator
base-splice-git-ref:
upgrade-splice-git-ref:
cluster: scratchneta
link

[isegall-da]

Failed, missing the stack files. Added and retrying: https://app.circleci.com/pipelines/github/DACH-NY/canton-network-internal/13108/workflows/efdd1ef7-7476-4a22-b6db-12a68aed11a6

[isegall-da]

Now failing on:

Back-off pulling image "ghcr.io/digital-asset/decentralized-canton-sync-dev/docker/pulumi-kubernetes-operator:v0.3.21-snapshot.20250606.142.0.v20eb2b3b"

Why is it thinking that it's a snapshot? 🤔

[isegall-da]

Why is it thinking that it's a snapshot? 🤔

Ah, because it's a commit on the PR branch, and not on the release line.
Two options: either I push this snapshot, or I merge this and try HDM from the release line. I'll try the former, and keep this as a PR that I can continue iterating on and eventually merge while everybody's out on a long weekend...

[isegall-da]

😢
publish-internal-release failed with:
/home/********/project/splice/build-tools/get-release-if-on-release-branch.sh: No such file or directory

Backporting that from main.

[isegall-da]

OK, images pushed now. Here we go again: https://app.circleci.com/pipelines/github/DACH-NY/canton-network-internal/13123/workflows/9dc5e007-9fac-49b6-8192-bf43c9871798

[isegall-da]

Woohoo, the HDM test has passed deploying 0.3.21 and triggering migration. Seems enough to merge this!