fix: do not strict new created dialog name to be lowercase

[zhixzhan]

Description

1. When create a dialog Hello now will create same case sensitive files:

dialogs/Hello/{Hello.dialog, Hello.lg, Hello.lu}

previous will created files:

dialogs/hello/{hello.dialog, hello.lg, hello.lu}

2. Validation is case insensitive (addressed via fix: validate skill empty & add duplicate dialog #3686 )

Task Item

close #3814

Screenshots

[coveralls]

Coverage remained the same at 56.422% when pulling b8394e2 on zhixzhan/dialog-naming-case into f1b8b4e on main.