[M108 Migration] Reset EWebContext ptr in CookieManager during EWebContext destroyed

[M108 Migration] Reset EWebContext ptr in CookieManager during EWebContext destroyed

CookieManager accesses EWebContext when it handles cookie storage,
but it has longer life cycle than EWebContext. To prevent accessing the
destroyed EWebContext, this patch resets the pointer of EWebContext in
CookieManager when EWebContext is destroyed.

Chromium supports only SQLite based persistent cookie storage.
This patch deprecates an enumeration for text file based cookie storage,
EWK_COOKIE_PERSISTENT_STORAGE_TEXT.

Reference:
https://review.tizen.org/gerrit/c/281416
https://review.tizen.org/gerrit/c/280780

Change-Id: I180b12b6929aac1d991d2c942f1eaf6780de992f
Signed-off-by: Bakka Uday Kiran <b.kiran@samsung.com>