Migrate some tests to the new htmlRunner

Fix events.get_timeStamp (was events.get_timestamp, wrong casing).

Rename `newRunner` to `htmlRunner`.

move tests to src/tests (from src/browser/tests). src/runtime and possibly other
parts might want to have html tests too.

src/main.zig

@@ -796,7 +796,7 @@ fn testHTTPHandler(req: *std.http.Server.Request) !void {
         });
     }
 
-    if (std.mem.startsWith(u8, path, "/src/browser/tests/")) {
+    if (std.mem.startsWith(u8, path, "/src/tests/")) {
         // strip off leading / so that it's relative to CWD
         return TestHTTPServer.sendFile(req, path[1..]);
     }