Fix problems with output filters in StandardOutputView plugin

Summary:
Multiple problems with filters in StandardOutputView plugin including
discrepancy between output view, filter and proxy model were caused by
using the tab index instead of view index as a key to m_filters and
m_proxyModels maps.

BUG: 343124

Reviewers: KDevelop, brauch

Subscribers: kfunk, brauch, kdevelop-devel

Tags: KDevelop

Differential Revision: https://phabricator.kde.org/D14750