helm: upgrade cert-manager from v1.12.6 to v1.15.0

[daniel-weisse]

Context

Proposed change(s)

• Upgrade cert-manager to v1.15.0

Checklist

• Run the E2E tests that are relevant to this PR's changes
  • Upgrade test
  • e2e test
• Update docs
• Add labels (e.g., for changelog category)
• Is PR title adequate for changelog?
• Link to Milestone

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[burgerdev]

Chart import lgtm.

1. This probably needs a changelog entry because of the breaking changes from 1.12 to 1.13.
2. Do we need to consider the upgrade instructions (reset-then-reuse-values)? I wonder whether we might miss something when we just apply the charts.

[github-actions]

Coverage report

Package	Old	New	Trend
internal/constellation/helm	33.80%	33.80%	🚧

[daniel-weisse]

We don't have any featureGates set, so the breaking change is not an issue.
As for the reset-then-reuse-values, I think @derpsteb probably knows best how the helm charts are configured for upgrade, but I know that we disable value reuse, so we should always use the values from the embedded chart when applying upgrades

[burgerdev]

Number 4 of the breaking changes might affect users, though.

[daniel-weisse]

We can add some notes in the changelog