KO-99: Bumped operator-sdk version from 1.10.1 to 1.28.0

[abhishekdwivedi3060]

• Bumped operator-sdk version to 1.28.0

• Tested AKO OLM bundle created using operator-sdk 1.28.0 on k8s 1.18

• Task deferred: New directory structure as per go/v4-alpha introduced in operator-sdk 1.28.0

• Ref: 1. https://sdk.operatorframework.io/docs/upgrading-sdk-version/v1.28.0/
  2. ⚠️ go/v4-alpha: change the layout to follow Golang Standards kubernetes-sigs/kubebuilder#2985
  3. https://github.com/golang-standards/project-layout

abhisek@abhi-master:~$ k version
Client Version: version.Info{Major:"1", Minor:"18", GitVersion:"v1.18.0", GitCommit:"9e991415386e4cf155a24b1da15becaa390438d8", GitTreeState:"clean", BuildDate:"2020-03-25T14:58:59Z", GoVersion:"go1.13.8", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"18", GitVersion:"v1.18.20", GitCommit:"1f3e19b7beb1cc0110255668c4238ed63dadb7ad", GitTreeState:"clean", BuildDate:"2021-06-16T12:51:17Z", GoVersion:"go1.13.15", Compiler:"gc", Platform:"linux/amd64"}
abhisek@abhi-master:~$ k get pod
NAME                                                              READY   STATUS      RESTARTS   AGE
28c401de52fd34b0f5b7b50430eabd1cd92608f1228405c8afac83ad5dtsl77   0/1     Completed   0          24m
aerocluster-0-0                                                   1/1     Running     0          15m
aerocluster-0-1                                                   1/1     Running     0          15m
aerospike-operator-controller-manager-7d44d894fb-g5whc            2/2     Running     0          23m
aerospike-operator-controller-manager-7d44d894fb-kqbcb            2/2     Running     0          23m
ekdwivedi3060-aerospike-kubernetes-operator-bundle-2-5-0-latest   1/1     Running     0          24m