chore: upgrade Go version to 1.27 and modernize idioms (#974)

* chore: upgrade Go version to 1.27 and modernize idioms

- Update go.mod to Go 1.27 and run go mod tidy
- Run go fix and modernize analyzer passes
- Modernize slice lookups with slices.Contains and map copies with maps.Copy
- Format repository code with go fmt

Signed-off-by: Matthias Bertschy <matthias.bertschy@gmail.com>

* build: bump Go version to 1.27 in Dockerfiles and GitHub Actions

Signed-off-by: Matthias Bertschy <matthias.bertschy@gmail.com>

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Signed-off-by: Matthias Bertschy <matthias.bertschy@gmail.com>