[GTK][WPE] missing URI for injected user scripts and style sheets

Reviewed by Adrian Perez de Castro.

User scripts/style sheets without the URI are not visible in WebInspector.

With this change the URI of injected user scripts/style sheets are generated as: user-script:incremented_identifier user-style:incremented_identifier

LayoutTests/userscripts/window-onerror-for-isolated-world-1-expected.txt:
LayoutTests/userscripts/window-onerror-for-isolated-world-2-expected.txt:
LayoutTests/userscripts/window-onerror-for-isolated-world-3-expected.txt:
Source/WebCore/Sources.txt:
Source/WebCore/WebCore.xcodeproj/project.pbxproj:
Source/WebCore/page/UserScript.cpp: Copied from Source/WebKit/UIProcess/API/APIUserScript.cpp. (WebCore::generateUniqueURL): (WebCore::UserScript::UserScript):
Source/WebCore/page/UserScript.h: (WebCore::UserScript::UserScript): Deleted.
Source/WebCore/page/UserStyleSheet.cpp: Copied from Source/WebKit/UIProcess/API/APIUserScript.cpp. (WebCore::generateUniqueURL): (WebCore::UserStyleSheet::UserStyleSheet):
Source/WebCore/page/UserStyleSheet.h:
Source/WebCore/page/WorkerNavigator.cpp:
Source/WebKit/UIProcess/API/APIUserScript.cpp: (API::UserScript::generateUniqueURL): Deleted.
Source/WebKit/UIProcess/API/APIUserScript.h:
Source/WebKit/UIProcess/API/APIUserStyleSheet.cpp: (API::UserStyleSheet::generateUniqueURL): Deleted.
Source/WebKit/UIProcess/API/APIUserStyleSheet.h:
Source/WebKit/UIProcess/API/C/WKUserScriptRef.cpp: (WKUserScriptCreateWithSource):

WebPlatformForEmbedded / WPEWebKit