Use document index to infer a name for a newly created client-side class or routine

[isc-bsaviano]

This PR fixes #1715 by implementing a new mechanism for inferring the name of a newly created client-side class or routine. The previous mechanism used the objectscript.export settings and was buggy, so I removed it. However, feedback from some users has indicated that this feature was really helpful. This is my attempt to bring it back in a more reliable way.

[isc-klu]

It looks like docNamePath and startOfDocName don’t depend on the outer loop (L457). Since their values stay the same for all i, recomputing them each time adds unnecessary work and makes the logic a bit harder to follow.

It might be clearer—and more efficient—to compute all of the “leading path segments that don’t contribute to the document name” once up front (and possibly cache that across inferDocName calls if it makes sense).

With that in place, the structure of the function could look something like:

export function inferDocName(uri: vscode.Uri): string | undefined {
  // check ext
  ...
  // compute "leadings"
  const leadings = new Set(index.uris.map(leading))
  // find the first leading
  for (const leading of leadings) {
    if uri.path.startsWith(leading) {
      return result = uri.path.slice(leading.length).replaceAll("/", ".") + fileExt;
    }
  }
}

function leading(docUri: vscode.URI): string {
  ...
}

[isc-bsaviano]

Good suggestion KC!