Inconsistency in allowed characters for a password

[henry.wright]

When a user attempts to reset his or her password using the facility on the front-end, they are able to use the \ character in their new password.

When a user attempts to change their password at wp-admin > Users > Profile, they aren't able to use the \ character in their password.

This feels like an inconsistency.

Further, I noticed whitespace is stripped from the beginning and end of the password string when using the change password facility at wp-admin > Users > Profile. Note trim() isn't used in the password reset facility on the front-end.

[henry.wright]

Related #35500