[M120 Migration][VD]Fix wrong key and text issue

[M120 Migration][VD]Fix wrong key and text issue

1.[VD]Fix wrong key issue

The keys after IME filtered, WebEngine can only receive text on
callback, then WebEngine make fake key event with the text;
compared with the original key event, the fake event lost many
key properties(such as without the modifiers).

If get the DomKey from DomCode, will get wrong key,such as:
input uppercase letter "A" with IME, the key of key up event is lowercase key "a";
input "+" with IME, the key of key up event is "=".

So keep same with M94, if there is no key value, return empty directly,
don't get the DomKey from DomCode, for avoid getting wrong key value.

2.[EFL] Fix wrong text and wrong unmodifiedText issue

For EFL key event,keep same with M94, should get the text and unmodifiedText
from evt->string, not from evt->key.

On most case, the evt->string same with the evt->key;
but on some case, the evt->string may not same with the evt->key, such as:
when number lock, press the number key on the Numeric keypad area of the
usb-keboard, the evt->string is empty, it not same with the evt->key.
And press the number key when number lock, should not show the number.

refer:
https://review.tizen.org/gerrit/#/c/295521/
https://review.tizen.org/gerrit/#/c/295328/

Change-Id: I114db7a08244ef9ce38a18ac43c3f2f9501813b0
Signed-off-by: fang fengrong <fr.fang@samsung.com>