Internal Optimization: List keys in SecretStorage will become available

[tnaum-ms]

Revisit https://code.visualstudio.com/updates/v1_105#_list-keys-in-secretstorage

VS Code will expose the API to list all keys that an extension has stored in Secret Storage.

export function activate(context: ExtensionContext) {
  const keys: string[] = await context.secrets.keys();

  const value = await context.secrets.get(keys[0]); // a value that exists
}

We can/could use it to optimize the way we store / delete secrets.

@sevoku I didn't assign any milestone. Please triage as you see fit. For vscode-documentdb it will be some time around the 0.10.0 release.