Rename WebContents related delegate classes inside tizen_src

Rename WebContents related delegate classes inside tizen_src

There are around three to four |WebContents**Delegate| classes inside
tizen_src; this causes confusion during debugging the codeflow.

This commit improves readability/understandability by making below changes:
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[1] Rename WebContentsViewDelegateEwk to WebContentsViewDelegateEfl

A class inside tizen_src implementing a opensource public class should have
classname with 'Efl' suffix (instead of 'Ewk').

WebContentsImpl : WebContentsDelegate => WebContentsDelegateEfl
WebContentsViewAura : WebContentsViewDelegate => WebContentsViewDelegateEfl
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[2] Rename WebContentsEflDelegate to WebViewDelegateEfl

Currently WebContentsEflDelegate is created in EWebView and been accessed by
two other classes, hence rename it to WebViewDelegateEfl and make EWebView
own it. Other classes will just use its pointer to route delegate calls.

EWebView                       \
WebContentsImplEfl           ---  WebViewDelegateEfl (owned by EWebView)
WebContentsViewAuraHelperEfl   /
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After this patch, there exists only 2 |WebContents*DelegateEfl| classes, i.e
WebContentsDelegateEfl and WebContentsViewDelegateEfl, both are inherited
from opensource public classes respectively. Other delegate classnames will
not have prefix 'WebContents'.

Change-Id: I5dafc3f858aed6c9affc81d89a3b8512bfcfc6a9
Signed-off-by: Gajendra N <gajendra.n@samsung.com>