Proxy path fixes (#4548)

* Fix issue where HTTP error status codes are not read.

* Fix issues surrounding sessions when accessed from a proxy.

- Updated vscode args to match latest upstream.
- Fixed issues surrounding trailing slashes affecting base paths.
- Updated cookie names to better match upstream's usage, debuggability.

* Bump vendor.

* Update tests.

* Fix issue where tests lack cookie key.

Co-authored-by: Asher <ash@coder.com>

src/common/http.ts

@@ -13,8 +13,12 @@ export enum HttpCode {
  * used in the HTTP response.
  */
 export class HttpError extends Error {
-  public constructor(message: string, public readonly status: HttpCode, public readonly details?: object) {
+  public constructor(message: string, public readonly statusCode: HttpCode, public readonly details?: object) {
     super(message)
     this.name = this.constructor.name
   }
 }
+
+export enum CookieKeys {
+  Session = "code-server-session",
+}