[aider assisted] MM-61888: Add ClientSideUserIds field to MetricsSettings (#30127)

We add a new config setting to allow the admin to set a fixed
list of userIDs to track for all client side webapp metrics.

This gives the admin to get a deeper look at how the application
is behaving for a single user.

A new section in the system console is also added for the user
to edit this setting from the UI.

https://mattermost.atlassian.net/browse/MM-61888

```release-note
A new config setting MetricsSettings.ClientSideUserIds is added
where you can set the user ids you want to track for client side webapp
metrics.
```

* fix lint errors

```release-note
NONE
```

* fixing tests

```release-note
NONE
```

server/channels/api4/metrics_test.go

@@ -91,7 +91,11 @@ func TestSubmitMetrics(t *testing.T) {
 
 	t.Run("metrics enabled and valid", func(t *testing.T) {
 		metricsMock := setupMetricsMock()
-		metricsMock.On("IncrementClientLongTasks", mock.AnythingOfType("string"), mock.AnythingOfType("string"), mock.AnythingOfType("float64")).Return()
+		metricsMock.On("IncrementClientLongTasks",
+			mock.AnythingOfType("string"),
+			mock.AnythingOfType("string"),
+			mock.AnythingOfType("string"),
+			mock.AnythingOfType("float64")).Return()
 
 		platform.RegisterMetricsInterface(func(_ *platform.PlatformService, _, _ string) einterfaces.MetricsInterface {
 			return metricsMock
@@ -159,7 +163,11 @@ func TestSubmitMetrics(t *testing.T) {
 
 	t.Run("metrics recorded for API errors", func(t *testing.T) {
 		metricsMock := setupMetricsMock()
-		metricsMock.On("IncrementClientLongTasks", mock.AnythingOfType("string"), mock.AnythingOfType("string"), mock.AnythingOfType("float64")).Return()
+		metricsMock.On("IncrementClientLongTasks",
+			mock.AnythingOfType("string"),
+			mock.AnythingOfType("string"),
+			mock.AnythingOfType("string"),
+			mock.AnythingOfType("float64")).Return()
 
 		platform.RegisterMetricsInterface(func(_ *platform.PlatformService, _, _ string) einterfaces.MetricsInterface {
 			return metricsMock
@@ -190,7 +198,11 @@ func TestSubmitMetrics(t *testing.T) {
 
 	t.Run("metrics recorded for URL length limit errors", func(t *testing.T) {
 		metricsMock := setupMetricsMock()
-		metricsMock.On("IncrementClientLongTasks", mock.AnythingOfType("string"), mock.AnythingOfType("string"), mock.AnythingOfType("float64")).Return()
+		metricsMock.On("IncrementClientLongTasks",
+			mock.AnythingOfType("string"),
+			mock.AnythingOfType("string"),
+			mock.AnythingOfType("string"),
+			mock.AnythingOfType("float64")).Return()
 
 		platform.RegisterMetricsInterface(func(_ *platform.PlatformService, _, _ string) einterfaces.MetricsInterface {
 			return metricsMock