Vcs: Dissolve VcsBaseOptionsPage intermediate hierarchy level

It's effectively setting only three properties nowadays, not enough
to justify a case of reuse-by-inheritance anymore.

Change-Id: Ia0aedbd0dc460a70bed580a3402cf928c7221a77
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/perforce/settingspage.cpp

@@ -118,10 +118,11 @@ void SettingsPageWidget::setStatusError(const QString &t)
 }
 
 SettingsPage::SettingsPage(QObject *parent)
-    : VcsBaseOptionsPage(parent)
+    : Core::IOptionsPage(parent)
 {
     setId(VcsBase::Constants::VCS_ID_PERFORCE);
     setDisplayName(tr("Perforce"));
+    setCategory(VcsBase::Constants::VCS_SETTINGS_CATEGORY);
 }
 
 SettingsPage::~SettingsPage()

src/plugins/perforce/settingspage.h

@@ -25,9 +25,7 @@
 
 #pragma once
 
-#include <QWidget>
-
-#include <vcsbase/vcsbaseoptionspage.h>
+#include <coreplugin/dialogs/ioptionspage.h>
 
 #include "ui_settingspage.h"
 
@@ -59,7 +57,7 @@ private:
     PerforceChecker *m_checker = nullptr;
 };
 
-class SettingsPage : public VcsBase::VcsBaseOptionsPage
+class SettingsPage : public Core::IOptionsPage
 {
     Q_OBJECT