Convert valid email addresses to a chip.

There is a user visible side affect of this change:
1) Assume you have a recipient <ekinoguz@google.com> in your contact
list.
2.1) Before this change, typing "ekinoguz@google.co" and focusing out
from RecipientEditTextView will not convert "ekinoguz@google.co" to a
chip.
2.2) After this change, it will convert to a chip.

Converting to a chip will make the behavior consistent with a non-valid
email address. As an example, currently, typing "ekinoguz@google.c" or
"ekinoguz@google." and focusing out from view converts string to a chip
already. But typing a valid email address (in format of *@*.* where part
after . has at least 2 characters) and focusing out does not convert
string to a chip. Current change will make this consistent.

Follow-up to ag/1216979, which addresses the same bug but got reverted
due to b/30352337.

BUG: 30106082
Change-Id: I6ac30783667af5cef6f53f3ffb89b935e1905502