Add commit field to pipeline GraphQL type

What does this MR do and why?

This MR;

• adds the commit (Types::CommitType) GraphQL field to Types::Ci::PipelineType
• adds the full_title GraphQL field to Types::CommitType

Related to #341093 (closed), (original: #327196 (closed))

Screenshots or screen recordings

How to set up and validate locally

Open http://gdk.test:3000/-/graphql-explorer and use;

query getPipeline($fullPath: ID!, $sha: String!) {
  project(fullPath: $fullPath) {
    pipeline(sha: $sha) {
      commit {
        fullTitle
      }
    }
  }
}

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.