silence clang-tidy warning and simplify enum

The warning is plain wrong, the function isn't detected by qt if it is
in an anonymous namespace and it is used.
Enum automatically counts up so there is no need to manually set these
values.

src/models/eventmodel.cpp

@@ -12,7 +12,9 @@
 
 #include <QSet>
 
-static bool operator<(const EventModel::Process& process, qint32 pid)
+// silence clang warnings
+// NOLINTNEXTLINE(misc-use-anonymous-namespace)
+[[maybe_unused]] static bool operator<(const EventModel::Process& process, qint32 pid)
 {
     return process.pid < pid;
 }
@@ -21,12 +23,12 @@ namespace {
 enum class Tag : quint8
 {
     Invalid = 0,
-    Root = 1,
-    Overview = 2,
-    Cpus = 3,
-    Processes = 4,
-    Threads = 5,
-    Tracepoints = 6,
+    Root,
+    Overview,
+    Cpus,
+    Processes,
+    Threads,
+    Tracepoints,
 };
 
 enum OverViewRow : quint8