Convert uses of $_SESSION in ViewsExecutable

Problem/Motivation

Now that Symfony sessions are in place and available from $request->getSession()</span>, views should be updated that it uses that instead of accessing <code>$_SESSION directly.

This issue is was extracted from #2473875: Convert uses of $_SESSION to symfony session retrieved from the request to improve reviewability.

Proposed resolution

Remaining tasks

User interface changes

None

API changes

None