feat: emit an event when accessing restricted path in File System Access API

[codebytere]

Description of Change

Closes #42459

More closely match upstream spec behavior when File System Access API attempts to open a file or directory in a blocked path. Now, a file-system-access-restricted event is emitted on session when a user attempts to access a restricted path:

{
  origin: 'https://www.buzzfeed.com/',
  isDirectory: true,
  path: '/Users/codebytere/Downloads'
}

Developers can then decide how to proceed.

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: Aligned failure pathway in File System Access API with upstream when attempting to open a file or directory in a blocked path.

[MarshallOfSound]

Electron has historically never contained user-facing UI. It introduces problems around messaging, UI style, translations, etc.

Is this not something that apps can understand and implement themselves?

[codebytere]

@MarshallOfSound we have for other web platform APIs in specific circumstances, but - at the moment we log-only, which i don't think is a good experience either, for reasons in part outlined by the issue author. We could potentially emit an event?

[jkleinsc]

@codebytere we emit events for device choosers from Session (eg https://www.electronjs.org/docs/latest/api/session#event-select-usb-device) when upstream would should a dialog.

[jkleinsc]

We should emit an event and let developers handle this much like we do for the device choosers.

[codebytere]

@jkleinsc ah good shout - i'll do that!

[marcello3d]

would there be a way to allow the restricted directory to be used? because currently this doesn't let you choose ~/Downloads on macOS if we want our web app to save multiple files in there

[codebytere]

@marcello3d reworked it a bit - a69e079 should enable that!

[jkleinsc]

Docs need some clarification.

[jkleinsc]

The docs should explain what the different actions mean.