Add "TtyTerm" terminal type to TerminalDxe

Add "TtyTerm" terminal type to TerminalDxe

This patch a adds new terminal type, TtyTerm, to TerminalDxe.  This terminal
type provides a place to add support for various *nix terminals that don't
behave like standard VT terminals.  The goal is to 'just work' with as many
terminals as possible, rather than properly emulating any one specific
terminal.

Signed-off-by: Roy Franz <roy.franz@linaro.org>
Contributed-under: TianoCore Contribution Agreement 1.0
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Feng Tian <feng.tian@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17895 6f19259b-4bc3-4df7-8a09-765794883524