Split ContextMenuExtension::AnalyzeGroup to File/Project groups

Summary: This patch is required for D5044 revision (Move "Analyze" menu items into "Code" menu).

Test Plan: Tested with master branch

Reviewers: KDevelop, mwolff, apol

Reviewed By: KDevelop, mwolff

Subscribers: kdevelop-devel

Differential Revision: https://phabricator.kde.org/D5043