bump: update golang to `1.22`

[Go 1.22](https://go.dev/blog/go1.22) is released with [release notes](https://go.dev/doc/go1.22)!

It is time to bump up golang version to `1.22` by updating

- `go.mod` for `oras` and its E2E tests.
- GitHub Actions
- Dockerfile
- `snapcraft.yaml`

Reference:
- #1074