ResourceLoadStatistics logic does not understand custom WebsiteData stores

ResourceLoadStatistics logic does not understand custom WebsiteData stores
https://bugs.webkit.org/show_bug.cgi?id=176037
<rdar://problem/33338238>

Reviewed by Alex Christensen.

Source/WebKit:

The NetworkProcess::updateCookiePartitioningForTopPrivatelyOwnedDomains always notifies the default website
data store about observations it has made. This should be revised so that WebKit clients that register
custom data stores through the WKWebsiteDataStores API can be assured that observations made in one session
do not manipulate data from another session.

* NetworkProcess/NetworkProcess.cpp:
(WebKit::NetworkProcess::updateCookiePartitioningForTopPrivatelyOwnedDomains): Use the passed sessionID to locate
the correct NetworkStorageSession to notify about the new partitioning data.
* NetworkProcess/NetworkProcess.h:
* NetworkProcess/NetworkProcess.messages.in: Accept new argument.
* UIProcess/WebsiteData/WebsiteDataStore.cpp:
(WebKit::WebsiteDataStore::updateCookiePartitioningForTopPrivatelyOwnedDomains): Include the WebsiteDataStore's
session ID in the message to update cookie partition data.

Tools:

* TestWebKitAPI/Tests/WebKitCocoa/WebsiteDataStoreCustomPaths.mm:
(TEST): Update for ResourceLoadStatistics directories.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@221337 268f45cc-cd09-0410-ab3c-d52691b4dbfc