Add policy name to ScanExecutionPolicyCommit mutation

What does this MR do?

Addresses #339794 (closed)

This MR adds a new argument name to ScanExecutionPolicyCommit mutation. Since we do not have a reference to a policy in the yaml file in policy project, the name of the policy is considered as an unique identifier. But if the name of the policy need to be updated, the old name has to mentioned explicitly to make it work.

Screenshots or Screencasts (strongly suggested)

Before	After

Update policy name:

Different name while creating policy:

Mutation

mutation createPolicy{
  scanExecutionPolicyCommit(input:{
    projectPath:"root/rails-demo",
    operationMode:REPLACE,
    name: Policy
    policyYaml: "name: Updated Policy\ntype: scan_execution_policy\ndescription: This policy enforces pipeline configuration to have a job with secret detection scan\nenabled: true\nrules:\n- type: pipeline\n  branches: \n    - master\nactions:\n- scan: secret_detection"
  }) {
    clientMutationId
    branch
    errors
  }
} 

Response

{
  "data": {
    "scanExecutionPolicyCommit": {
      "clientMutationId": null,
      "branch": "update-policy-1624288106",
      "errors": []
    }
  }
} 

How to setup and validate locally (strongly suggested)

Does this MR meet the acceptance criteria?

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