Replace `find` with `contains/has` where applicable

[AThousandShips]

• Replaces find(...) != -1, find(...) > -1, find(...) >= 0 with contains for String
• Replaces find(...) == -1, find(...) < 0 with !contains for String
• Replaces find(...) != -1, find(...) > -1, find(...) >= 0 with has for containers
• Replaces find(...) == -1, find(...) < 0 with !has for containers

Split into four commits for review to make it easier to compare each type, to check the replacements are appropriate

[Chaosus]

Guess this line could be changed too (after https://github.com/godotengine/godot/commit/d8aa2c65a9f857e86d0c1fc1cc6b95b8ccf23099): https://github.com/godotengine/godot/blob/d8aa2c65a9f857e86d0c1fc1cc6b95b8ccf23099/editor/connections_dialog.cpp#L285

[AThousandShips]

That's findn that's different, that's covered here:

• https://github.com/godotengine/godot/pull/91611

[akien-mga]

Thanks!

[AThousandShips]

Thank you!