{{PAGESIZE:{{FULLPAGENAME}}}}, {{{{FULLPAGENAME}}}} not outdated

Previously, when parsing {{PAGESIZE:{{FULLPAGENAME}}}} or
{{ {{FULLPAGENAME}} }} (a self-transclusion), we used the
version currently in the db, which is outdated because
the moment we save the page there will be a new version.

This often causes confusion when testing templates that
often have examples of template use in the doc section
which would be one version out of date.

This change causes those variables to give results for
the most recent version of the page. For self-templates
that's done by reparsing the page after save. For
self page sizes this is done by taking the size
of the input to Parser::parse.

Note that {{subst:PAGESIZE:{{subst:FULLPAGENAME}}}}
will still yield previous revision like before.

bug: 39590
Change-Id: Idfac13de37d05317f65e4131534543e66cf74873