Diagnostics from remote Docker Hack LSP are mapped to the first workspace folder

When using hack.remote.enabled with Docker in a multi-root workspace, Hack
diagnostics are mapped to workspaceFolders[0] instead of the workspace folder
that corresponds to hack.remote.workspacePath.

In this repro, the real Hack error is in hack/type_error.hack, but VS Code
reports it against not-hack/type_error.hack.

Code reference

https://github.com/slackhq/vscode-hack/blob/559abd48722fc16e2fb27c5874259563d8f55b66/src/Config.ts#L55-L62

Note how it takes workspaceFolders![0]

Expected

The diagnostic points to:

hack/type_error.hack

Actual

The diagnostic points to:

not-hack/type_error.hack

That file does not exist.

Notes

If the hack folder is moved to the first position in the workspace file and
the window is reloaded, the same diagnostic points to the correct file.

Repro script

Run this script in an empty directory to recreate a minimal reproduction case.

#!/usr/bin/env sh
set -eu

root=hack-vscode-wrong-root-repro
rm -rf "$root"
mkdir -p "$root/not-hack" "$root/hack"

cat > "$root/hack-vscode-wrong-root-repro.code-workspace" <<'JSON'
{
  "folders": [
    {
      "name": "not-hack",
      "path": "not-hack"
    },
    {
      "name": "hack",
      "path": "hack"
    }
  ],
  "settings": {
    "hack.remote.docker.containerName": "hack-vscode-wrong-root-repro-hack-1",
    "hack.remote.enabled": true,
    "hack.remote.type": "docker",
    "hack.remote.workspacePath": "/mnt/project"
  }
}
JSON

cat > "$root/docker-compose.yml" <<'YAML'
name: hack-vscode-wrong-root-repro

services:
  hack:
    image: hhvm/hhvm:latest
    working_dir: /mnt/project
    command: sleep infinity
    volumes:
      - type: bind
        source: ./hack
        target: /mnt/project
YAML

touch "$root/not-hack/some_other_file.txt"
touch "$root/hack/.hhconfig"

cat > "$root/hack/type_error.hack" <<'HACK'
const string X = 0;
HACK

cd "$root"
docker compose up -d

Then open hack-vscode-wrong-root-repro.code-workspace in VS Code with the
Hack extension enabled.

Start at src/Config.ts lines 55-62, where the remote workspace mapping uses the first workspace folder. Run the supplied Docker multi-root reproduction and inspect how hack.remote.workspacePath is matched to a workspace folder. Done when the diagnostic for hack/type_error.hack is reported against that file even when the hack folder is not first.