chore(perf): Pre-allocate where possible (enable prealloc linter) (#88952)

* chore(perf): Pre-allocate where possible (enable prealloc linter)

Signed-off-by: Dave Henderson <dave.henderson@grafana.com>

* fix TestAlertManagers_buildRedactedAMs

Signed-off-by: Dave Henderson <dave.henderson@grafana.com>

* prealloc a slice that appeared after rebase

Signed-off-by: Dave Henderson <dave.henderson@grafana.com>

---------

Signed-off-by: Dave Henderson <dave.henderson@grafana.com>

pkg/services/sqlstore/migrations/external_alertmanagers.go

@@ -97,9 +97,8 @@ func (e externalAlertmanagerToDatasources) Exec(sess *xorm.Session, mg *migrator
 }
 
 func removeDuplicates(strs []string) []string {
-	var res []string
-	found := map[string]bool{}
-
+	found := make(map[string]bool, len(strs))
+	res := make([]string, 0, len(strs))
 	for _, str := range strs {
 		if found[str] {
 			continue

pkg/services/sqlstore/permissions/dashboard.go

@@ -435,8 +435,10 @@ func (f *accessControlDashboardPermissionFilter) nestedFoldersSelectors(permSele
 }
 
 func getAllowedUIDs(action string, user identity.Requester, scopePrefix string) []any {
-	var args []any
-	for _, uidScope := range user.GetPermissions()[action] {
+	uidScopes := user.GetPermissions()[action]
+
+	args := make([]any, 0, len(uidScopes))
+	for _, uidScope := range uidScopes {
 		if !strings.HasPrefix(uidScope, scopePrefix) {
 			continue
 		}