Store preview id for two weeks (#79972)
Create a file `.previewinfo` (like `.rscinfo`) to store the preview mode keys (which are stored in `prerender-manifest.json` and were previously changing on every single commit)
```
"preview": {
"previewModeId": "6ec938745bce9b5d51329802d1a9788a",
"previewModeSigningKey": "f3df5e714dd35c14fedb15b396566ae9530e058f5dde09a82b12941214d96c4d",
"previewModeEncryptionKey": "675f97882ebc73c55bc51903f4e5c8d3a17ac90108847ed1b1b90a46d84f368e"
}
```
