[core] Warn user when directly launching yt-dlp.exe

[seproDev]

IMPORTANT: PRs without the template will be CLOSED

Description of your pull request and other information

Detect if the user opened the standalone executable by double-clicking, and display a helpful error message.

Co-authored by Grub4K.

Template

Before submitting a pull request make sure you have:

• At least skimmed through contributing guidelines including yt-dlp coding conventions
• Searched the bugtracker for similar pull requests
• Checked the code with flake8 and ran relevant tests

In order to be accepted and merged into yt-dlp each piece of code must be in public domain or released under Unlicense. Check all of the following options that apply:

• I am the original author of this code and I am willing to release it under Unlicense
• I am not the original author of this code but it is in public domain or released under Unlicense (provide reliable evidence)

What is the purpose of your pull request?

• Fix or improvement to an extractor (Make sure to add/update tests)
• New extractor (Piracy websites will not be accepted)
• Core bug fix/improvement
• New feature (It is strongly recommended to open an issue first)

[Grub4K]

I think this is a good middle ground for giving the user a bit of a hint as to what to do next

[pukkandan]

This is awesome if the check is reliable. We don't need to error though. Why not launch into interactive mode as-if --config-location - has been passed?

[Grub4K]

I think people that would double click would kind of be overwhelmed by what --config-location - does. We would have to create more documentation for it, like relaying to README.md for how to use it:

Reading options from interactive input
Refer to the README for what options are available:
https://github.com/yt-dlp/yt-dlp#readme
Press Ctrl+Z and confirm with enter to stop entering options.

Alternatively, we could also have them enter -a -, which is easier to understand:

Please enter all the URLs to download, separated by a space or newline.
Press Ctrl+Z and confirm with enter to stop entering URLs.

We also have to care with what CWD we are at; for example C:\Windows\System32\ might be problematic.
At that point I think it might make more sense to direct them to using the shell instead.

[seproDev]

if the check is reliable

I tested this on both Windows 11 and 7 with py2exe, PyInstaller onefile, and PyInstaller onedir builds. In my testing, this worked reliably.