refactor: rename files to follow Go convention

test/error_strings_custom_functions_test.go

@@ -0,0 +1,15 @@
+package test
+
+import (
+	"testing"
+
+	"github.com/mgechev/revive/lint"
+	"github.com/mgechev/revive/rule"
+)
+
+func TestErrorStringsWithCustomFunctions(t *testing.T) {
+	args := []any{"pkgErrors.Wrap"}
+	testRule(t, "error_strings_with_custom_functions", &rule.ErrorStringsRule{}, &lint.RuleConfig{
+		Arguments: args,
+	})
+}