Add an error for exceeding refundable fee. (#134)

* Add errors for exceeding the refundable fee.

These have to be operation errors, as core is hard-wired to only return `txFAILED` on transaction failure and modifying this behavior is risky/slow.

* Remove `contractEventsSizeBytes` from `SorobanResources`.

This field is almost redundant and only helps to avoid apply-time error in the rare cases when the user sets the events resource, but forgets to set high enough refundable fee. It does, on the other hand, introduce another apply-time failure condition if the contracts emits a bit more events than expected (even if the refundable fee is high enough to cover that).

The total size of the events emitted is still governed by the network setting.

Stellar-transaction.x

@@ -814,10 +814,6 @@ struct SorobanResources
     uint32 readBytes;
     // The maximum number of bytes this transaction can write to ledger
     uint32 writeBytes;
-
-    // Maximum size of the contract events (serialized to XDR) this transaction
-    // can emit.
-    uint32 contractEventsSizeBytes;
 };
 
 // The transaction extension for Soroban.
@@ -1793,7 +1789,8 @@ enum InvokeHostFunctionResultCode
     INVOKE_HOST_FUNCTION_MALFORMED = -1,
     INVOKE_HOST_FUNCTION_TRAPPED = -2,
     INVOKE_HOST_FUNCTION_RESOURCE_LIMIT_EXCEEDED = -3,
-    INVOKE_HOST_FUNCTION_ENTRY_EXPIRED = -4
+    INVOKE_HOST_FUNCTION_ENTRY_EXPIRED = -4,
+    INVOKE_HOST_FUNCTION_INSUFFICIENT_REFUNDABLE_FEE = -5
 };
 
 union InvokeHostFunctionResult switch (InvokeHostFunctionResultCode code)
@@ -1804,6 +1801,7 @@ case INVOKE_HOST_FUNCTION_MALFORMED:
 case INVOKE_HOST_FUNCTION_TRAPPED:
 case INVOKE_HOST_FUNCTION_RESOURCE_LIMIT_EXCEEDED:
 case INVOKE_HOST_FUNCTION_ENTRY_EXPIRED:
+case INVOKE_HOST_FUNCTION_INSUFFICIENT_REFUNDABLE_FEE:
     void;
 };
 
@@ -1814,7 +1812,8 @@ enum BumpFootprintExpirationResultCode
 
     // codes considered as "failure" for the operation
     BUMP_FOOTPRINT_EXPIRATION_MALFORMED = -1,
-    BUMP_FOOTPRINT_EXPIRATION_RESOURCE_LIMIT_EXCEEDED = -2
+    BUMP_FOOTPRINT_EXPIRATION_RESOURCE_LIMIT_EXCEEDED = -2,
+    BUMP_FOOTPRINT_EXPIRATION_INSUFFICIENT_REFUNDABLE_FEE = -3
 };
 
 union BumpFootprintExpirationResult switch (BumpFootprintExpirationResultCode code)
@@ -1823,6 +1822,7 @@ case BUMP_FOOTPRINT_EXPIRATION_SUCCESS:
     void;
 case BUMP_FOOTPRINT_EXPIRATION_MALFORMED:
 case BUMP_FOOTPRINT_EXPIRATION_RESOURCE_LIMIT_EXCEEDED:
+case BUMP_FOOTPRINT_EXPIRATION_INSUFFICIENT_REFUNDABLE_FEE:
     void;
 };
 
@@ -1833,7 +1833,8 @@ enum RestoreFootprintResultCode
 
     // codes considered as "failure" for the operation
     RESTORE_FOOTPRINT_MALFORMED = -1,
-    RESTORE_FOOTPRINT_RESOURCE_LIMIT_EXCEEDED = -2
+    RESTORE_FOOTPRINT_RESOURCE_LIMIT_EXCEEDED = -2,
+    RESTORE_FOOTPRINT_INSUFFICIENT_REFUNDABLE_FEE = -3
 };
 
 union RestoreFootprintResult switch (RestoreFootprintResultCode code)
@@ -1842,6 +1843,7 @@ case RESTORE_FOOTPRINT_SUCCESS:
     void;
 case RESTORE_FOOTPRINT_MALFORMED:
 case RESTORE_FOOTPRINT_RESOURCE_LIMIT_EXCEEDED:
+case RESTORE_FOOTPRINT_INSUFFICIENT_REFUNDABLE_FEE:
     void;
 };