Provisioning: Improve validation by validating across all dashboard providers (#26742)

* Provisioning: check sanity across all dashboard readers

Signed-off-by: m.nabokikh <maksim.nabokikh@flant.com>

* Apply suggestions from code review

Co-authored-by: Emil Tullstedt <emil.tullstedt@grafana.com>
Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Refactor of duplicateValidator and fix issues according to commentaries

Signed-off-by: m.nabokikh <maksim.nabokikh@flant.com>

* Apply suggestions from code review

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Remove newDuplicateEntries function

Signed-off-by: m.nabokikh <maksim.nabokikh@flant.com>

* Change folderUid in logs to folderUID

Signed-off-by: m.nabokikh <maksim.nabokikh@flant.com>

* Restrict write access for readers, which are provisioning duplicate dashboards

Signed-off-by: m.nabokikh <maksim.nabokikh@flant.com>

* Fix file reader after rebasing onto master

Signed-off-by: m.nabokikh <maksim.nabokikh@flant.com>

* Apply suggestions from code review

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Format file_reader

Signed-off-by: m.nabokikh <maksim.nabokikh@flant.com>

* Apply suggestions from code review

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Apply suggestions from code review

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Fix lint problem

Signed-off-by: m.nabokikh <maksim.nabokikh@flant.com>

* Apply suggestions from code review

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>
Signed-off-by: m.nabokikh <maksim.nabokikh@flant.com>

Co-authored-by: Emil Tullstedt <emil.tullstedt@grafana.com>
Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>
Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>

pkg/services/provisioning/dashboards/file_reader_linux_test.go

@@ -25,7 +25,9 @@ func TestProvisionedSymlinkedFolder(t *testing.T) {
 	}
 
 	reader, err := NewDashboardFileReader(cfg, log.New("test-logger"), nil)
-	require.NoError(t, err)
+	if err != nil {
+		t.Error("expected err to be nil")
+	}
 
 	want, err := filepath.Abs(containingID)
 	require.NoError(t, err)