Forward experimental options in toolkit run (#16095)

# Description
I use `toolkit run` to test PRs or my own code. Passing experimental
options to it makes this nicer if you're trying to test that out.

# User-Facing Changes


You can pass `--experimental-options` to `toolkit run`.

# Tests + Formatting


- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`

# After Submitting

toolkit.nu

@@ -304,8 +304,18 @@ export def "check pr" [
 }
 
 # run Nushell from source with a right indicator
-export def run [] {
+export def run [
+    --experimental-options: oneof<list<string>, string> # enable or disable experimental options
+] {
+    let experimental_options_arg = $experimental_options 
+        | default [] 
+        | [$in] 
+        | flatten 
+        | str join "," 
+        | $"[($in)]"
+ 
     ^cargo run -- ...[
+        --experimental-options $experimental_options_arg
         -e "$env.PROMPT_COMMAND_RIGHT = $'(ansi magenta_reverse)trying Nushell inside Cargo(ansi reset)'"
     ]
 }