Add non-boolean feature flags support to the StaticProvider (#115085)

* initial commit

* add support of integerts

* finialise the static provider

* minor refactoring

* the rest

* revert:  the rest

* add new thiongs

* more tests added

* add ff parsing tests to check if types are handled correctly

* update tests according to recent changes

* address golint issues

* Update pkg/setting/setting_feature_toggles.go

Co-authored-by: Dave Henderson <dave.henderson@grafana.com>

* fix rebase issues

* addressing review comments

* add test cases for enterprise

* handle enterprise cases

* minor refactoring to make api a bit easier to debug

* make test names a bit more precise

* fix linter

* add openfeature sdk to goleak ignore in testutil

* Remove only boolean check in ff gen tests

* add non-boolean types top the doc in default.ini and doc string in FeatureFlag type

* apply remarks, add docs to sample.ini

* reflect changes in feature flags in the public grafana configuration doc

* fix doc formatting

* apply suggestions to the doc file

---------

Co-authored-by: Dave Henderson <dave.henderson@grafana.com>

pkg/util/testutil/context_test.go

@@ -15,7 +15,10 @@ import (
 func TestMain(m *testing.M) {
 	// make sure we don't leak goroutines after tests in this package have
 	// finished, which means we haven't leaked contexts either
-	goleak.VerifyTestMain(m)
+	// (Except for goroutines running specific functions. If possible we should fix this.)
+	goleak.VerifyTestMain(m,
+		goleak.IgnoreTopFunction("github.com/open-feature/go-sdk/openfeature.(*eventExecutor).startEventListener.func1.1"),
+	)
 }
 
 func TestTestContextFunc(t *testing.T) {