[PATCH 4/6] qa: Avoid deprecation warnings for QList/QSet conversions

[PATCH 4/6] qa: Avoid deprecation warnings for QList/QSet conversions

From 52209badc8e769e50aa3019b63689dda0e79e9d0 Mon Sep 17 00:00:00 2001
Bug: https://bugs.quassel-irc.org/issues/1544
Bug-Ubuntu: https://bugs.launchpad.net/quassel/+bug/1885436
Origin: upstream, https://github.com/quassel/quassel/pull/518
Origin: upstream, https://github.com/quassel/quassel/commit/52209badc8e769e50aa3019b63689dda0e79e9d0

Qt 5.14 deprecated the explicit functions for converting between
QSet and QList, preferring instead the use of range-based ctors.
Unfortunately, those ctors were only added in Qt 5.14, so we can't
use them when compiling against older versions.

Add a util function for QList->QSet to keep the version check in
a single place. Replace the other direction by using QSet::values().
In some cases, conversions could be avoided altogether, or an STL
container be used easily, so do that.

Gbp-Pq: Topic qt514
Gbp-Pq: Name 0004-qa-Avoid-deprecation-warnings-for-QList-QSet-convers.patch