Expose can_modify_blob_with_web_ide for GraphQL query

What does this MR do and why?

This MR reinstates backend changes as per this note: !159557 (comment 2023596851)

Frontend will be reinstated in %17.4 with !161349 (merged)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After
n/a	n/a

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Submit a GraphQL query to fetch a blob at a non-head ref to your local GDK:

    query {
      project(fullPath: "flightjs/Flight") {
        name
        repository {
          empty
          blobs(paths: "README.md", ref: "83c6aa31482b9076531ed3a880e75627fd6b335c") {
            nodes {
              name
              path
              canModifyBlob
              canModifyBlobWithWebIde
            }
          }
        }
      }
    }

Related to #410476 (closed)