node flag parsing strategy is backwards

[boneskull]

nodejs/node#34637 introduces a -u flag for node, which conflicts with Mocha's -u/--ui flag. I had expected Mocha would prefer its own options over node's where there was a conflict, but this is not the case--instead, Mocha explicitly whitelists -r/--require, which was previously the only known command-line flag shared between mocha and node.

To fix this, Mocha needs to change its strategy to detect its own options first, then attempt to detect if something is a node option. Currently, Mocha checks for node options first.

[boneskull]

cc @BethGriggs

[boneskull]

This does mean that if someone wants to use custom conditions w/ mocha, they need to use --conditions, not -u.

[boneskull]

Fix is in #4418