working on integration of multi-byte and multi-width runes (#4549)

* integrated runewidth for display management - fixed cursor movement for mutli-width char

* updated input and deletion of multi-byte chars

* fixed line history with some exceptions

* improved insert and add

* fixed issues with moving across lines

* end of line extra space tracking'

* saved changes

* fixed end of line issues with empty spaces

* worked some more

* worked on end of line

* fixed failed test

* fixed minor inserting bug

* fixed movement hotkeys

* adjusted hotkeys

* removed comments

* Update readline/buffer.go

Co-authored-by: Bruce MacDonald <brucewmacdonald@gmail.com>

* Update readline/buffer.go

Co-authored-by: Bruce MacDonald <brucewmacdonald@gmail.com>

* Update readline/buffer.go

Co-authored-by: Bruce MacDonald <brucewmacdonald@gmail.com>

* Update readline/buffer.go

Co-authored-by: Bruce MacDonald <brucewmacdonald@gmail.com>

* Update readline/buffer.go

Co-authored-by: Bruce MacDonald <brucewmacdonald@gmail.com>

* Update readline/buffer.go

Co-authored-by: Bruce MacDonald <brucewmacdonald@gmail.com>

* Update readline/buffer.go

Co-authored-by: Bruce MacDonald <brucewmacdonald@gmail.com>

* Update readline/buffer.go

Co-authored-by: Bruce MacDonald <brucewmacdonald@gmail.com>

* Update readline/buffer.go

Co-authored-by: Bruce MacDonald <brucewmacdonald@gmail.com>

* Update readline/buffer.go

Co-authored-by: Bruce MacDonald <brucewmacdonald@gmail.com>

* Update readline/buffer.go

Co-authored-by: Bruce MacDonald <brucewmacdonald@gmail.com>

* Update readline/buffer.go

Co-authored-by: Bruce MacDonald <brucewmacdonald@gmail.com>

* deleted comments and duplicate code

* removed duplicate code

* added comments, refactored add function to use addChar

* added helper to retrieve lineSpacing, renamed lineFlags for clarity

* fixed remove()

---------

Co-authored-by: Bruce MacDonald <brucewmacdonald@gmail.com>

readline/readline.go

@@ -150,7 +150,7 @@ func (i *Instance) Readline() (string, error) {
 					i.Pasting = false
 				}
 			case KeyDel:
-				if buf.Size() > 0 {
+				if buf.DisplaySize() > 0 {
 					buf.Delete()
 				}
 				metaDel = true
@@ -202,7 +202,7 @@ func (i *Instance) Readline() (string, error) {
 				buf.Add(' ')
 			}
 		case CharDelete:
-			if buf.Size() > 0 {
+			if buf.DisplaySize() > 0 {
 				buf.Delete()
 			} else {
 				return "", io.EOF