feat(wallet_ffi)!: add get_balance callback to wallet ffi (#3475)

Description
---
- Added get_balance callback to the wallet ffi callback handler that fires only if the balance has actually changed.
- Expanded the wallet ffi callback handler test framework to include a mock output manager request-response server.
- _**Update:** Added required methods and interfaces to the cucumber test framework._
- _**Update:** Fixed flaky wallet FFI cucumber tests._
- _**Update:** Fixed a bug in the wallet FFI cucumber test framework where the return type of `ref.types.ulonglong` did not correspond to the Rust return type and had a memory alignment problem._
- _**Update:** Fixed an issue whereby on a fast 8-core multi-tasking computer (e.g. AMD Ryzen 7 2700X) some of the wallet FFI cucumber tests did not complete properly after the test and went into an endless wait. The root cause of this issue has been traced down to incorrect use of synchronous calls to wallet FFI destroy methods where in actual fact those methods have async behaviour._
- _**Update:** Re-applied #3271._

~~The following anomaly exists when compiling the proposed `wallet_ffi/tests` module:~~
```
24 | use tari_wallet_ffi::callback_handler::CallbackHandler;
   |     ^^^^^^^^^^^^^^^ use of undeclared crate or module `tari_wallet_ffi`
```

_**Update**_ ~~Various code organizations have been tried, all with the same result. As an alternative, a working test and output manager service mock has been added into the test module in `callback_handler.rs`. Hopefully, the anomaly can be fixed. Duplicate code will be removed before the final commit.~~

Motivation and Context
---
- Mobile wallet efficiency.
- Resilient wallet FFI cucumber tests.

How Has This Been Tested?
---
- Expanded the current FFI `test_callback_handler` unit test.
- _**Update:** Ran all the wallet FFI cucumber tests to verify the new callback is working properly when using the wallet FFI library:_ 

```
2021-10-21T06:29:32.160Z callbackTransactionValidationComplete(9123501482775375388,0)
2021-10-21T06:29:32.161Z callbackBalanceUpdated: available = 0,  time locked = 0  pending incoming = 2000000 pending outgoing = 0
2021-10-21T06:29:32.263Z received Transaction with txID 14659183447022727953

...

2021-10-21T06:31:38.358Z Transaction with txID 14659183447022727953 was mined.
2021-10-21T06:31:38.358Z callbackBalanceUpdated: available = 2000000,  time locked = 2000000  pending incoming = 0 pending outgoing = 0
2021-10-21T06:31:38.359Z callbackTransactionValidationComplete(17755253868227079780,0)
```

applications/ffi_client/index.js

@@ -16,6 +16,8 @@ try {
   let err = ref.alloc(i32);
   // console.log(err);
 
+  let recoveryInProgress = ref.alloc(bool);
+
   console.log("Create Tor transport...");
   let tor = lib.transport_tor_create(
     "/ip4/127.0.0.1/tcp/9051",
@@ -79,17 +81,13 @@ try {
   const txCancelled = ffi.Callback("void", ["pointer"], function (ptr) {
     console.log("txCancelled: ", ptr);
   });
-  // callback_utxo_validation_complete: unsafe extern "C" fn(u64, u8),
-  const utxoValidation = ffi.Callback("void", [u64, u8], function (i, j) {
+  // callback_txo_validation_complete: unsafe extern "C" fn(u64, u8),
+  const txoValidation = ffi.Callback("void", [u64, u8], function (i, j) {
     console.log("utxoValidation: ", i, j);
   });
-  // callback_stxo_validation_complete: unsafe extern "C" fn(u64, u8),
-  const stxoValidation = ffi.Callback("void", [u64, u8], function (i, j) {
-    console.log("stxoValidation: ", i, j);
-  });
-  // callback_invalid_txo_validation_complete: unsafe extern "C" fn(u64, u8),
-  const itxoValidation = ffi.Callback("void", [u64, u8], function (i, j) {
-    console.log("itxoValidation: ", i, j);
+  // callback_balance_updated: unsafe extern "C" fn(*mut Balance),
+  const balanceUpdated = ffi.Callback("void", ["pointer"], function (ptr) {
+    console.log("balanceUpdated: ", ptr);
   });
   // callback_transaction_validation_complete: unsafe extern "C" fn(u64, u8),
   const txValidation = ffi.Callback("void", [u64, u8], function (i, j) {
@@ -117,11 +115,11 @@ try {
     directSendResult,
     safResult,
     txCancelled,
-    utxoValidation,
-    stxoValidation,
-    itxoValidation,
+    txoValidation,
+    balanceUpdated,
     txValidation,
     safsReceived,
+    recoveryInProgress,
     err
   );
 

base_layer/wallet_ffi/Cargo.toml

@@ -52,3 +52,4 @@ env_logger = "0.7.1"
 tari_key_manager = { version = "^0.11", path = "../key_manager" }
 tari_common_types = { version = "^0.11", path = "../../base_layer/common_types"}
 tari_test_utils = { version = "^0.11", path = "../../infrastructure/test_utils"}
+tari_service_framework = { path = "../../base_layer/service_framework" }