This PR fixes #140434

It's also a retake of @icepaq 's PR #141353, which has the discussion history.

This PR fixes the issue that the dates in the Extension details page are not formatted with the locale used in VS Code. The fix is fairly straightforward - get the locale string from vs/base/common/platform and pass it to Date.prototype.toLocaleString().

How to Test

1. Add the following member to product.json to enable extension marketplace in the OSS dev build

"extensionsGallery": {
  "serviceUrl": "https://marketplace.visualstudio.com/_apis/public/gallery",
  "cacheUrl": "https://vscode.blob.core.windows.net/gallery/index",
  "itemUrl": "https://marketplace.visualstudio.com/items"
},

2. Use "Configure Display Language" to change the locale used in VS Code. I've tested with en, es, and zh-cn, covering date formats MM/DD/YYYY, DD/MM/YYYY, and YYYY/MM/DD.
3. Go to the Extensions tab
4. Search for an extension (eg, "Prettier")
5. Ensure that the "Released on" and "Last updated" fields are rendered in the format specified by the locale.

	en	es	zh-cn
Format	MM/DD/YYYY	DD/MM/YYYY	YYYY/MM/DD