Move bold/italic parser tests from Parsoid's whitelist into upstream.

Parsoid has been maintaining a whitelist for tests where its output
diverges from the PHP parser.  This patch upstreams part of that whitelist,
creating separate PHP and Parsoid test cases to document in one place
where the parsed output diverges and why.  (Uses the recently-added
'php' and 'parsoid' options in parserTests.)

Change-Id: I07ca6ec1e039a2842c641fe543b2d92eb964d932
Merge "Move bold/italic parser tests from Parsoid's whitelist into upstream."