TF-2310 Use singleton for HiveCacheConfig to avoid creating multiple instance

test/features/caching/email_cache_client_test.dart

@@ -14,7 +14,7 @@ void main() {
   late EmailCacheClient emailCacheClient;
 
   setUpAll(() {
-    HiveCacheConfig().setUp(cachePath: Directory.current.path);
+    HiveCacheConfig.instance.setUp(cachePath: Directory.current.path);
   });
 
   setUp(() {

test/features/caching/mailbox_cache_client_test.dart

@@ -14,7 +14,7 @@ void main() {
   late MailboxCacheClient mailboxCacheClient;
 
   setUpAll(() {
-    HiveCacheConfig().setUp(cachePath: Directory.current.path);
+    HiveCacheConfig.instance.setUp(cachePath: Directory.current.path);
   });
 
   setUp(() {

test/features/offline_mode/woker_queue_test.dart

@@ -18,7 +18,7 @@ void main() {
   late MailboxStateWorkerQueue workerQueue;
 
   setUpAll(() {
-    HiveCacheConfig().setUp(cachePath: Directory.current.path);
+    HiveCacheConfig.instance.setUp(cachePath: Directory.current.path);
   });
 
   setUp(() {