MM-28859 Add feature flag managment system using split.io and remove viper. (#15954)

* Add feature flag managment system using split.io and remove viper.

* Fixing tests.

* Attempt to fix postgres tests.

* Fix watch filepath for advanced logging.

* Review fixes.

* Some error wrapping.

* Remove unessisary store interface.

* Desanitize SplitKey

* Simplify.

* Review feedback.

* Rename split mlog adatper to split logger.

* fsInner

* Style.

* Restore oldcfg test.

* Downgrading non-actionable feature flag errors to warnings.

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

vendor/github.com/splitio/go-split-commons/v2/tasks/interface.go

@@ -0,0 +1,53 @@
+package tasks
+
+import (
+	"sync"
+
+	"github.com/splitio/go-toolkit/v3/logging"
+)
+
+// Task interface
+type Task interface {
+	Start()
+	Stop(blocking bool) error
+	IsRunning() bool
+}
+
+// MultipleTask struct
+type MultipleTask struct {
+	tasks  []Task
+	logger logging.LoggerInterface
+	wg     *sync.WaitGroup
+}
+
+// IsRunning method
+func (m MultipleTask) IsRunning() bool {
+	for _, t := range m.tasks {
+		if t.IsRunning() {
+			return true
+		}
+	}
+	return false
+}
+
+// Start method
+func (m MultipleTask) Start() {
+	for _, t := range m.tasks {
+		m.wg.Add(1)
+		t.Start()
+	}
+}
+
+// Stop method
+func (m MultipleTask) Stop(blocking bool) error {
+	for _, t := range m.tasks {
+		go func(t Task) {
+			t.Stop(blocking)
+			m.wg.Done()
+		}(t)
+	}
+	if blocking {
+		m.wg.Wait()
+	}
+	return nil
+}