Batch API: better treat invalid transactions

[bogdan-rosianu]

Reasoning

• invalid transactions(code 400 from gateway) do not throw errors, so they are not properly treated

Proposed Changes

• if the result of the gateway call does not contain a txHash, mark the batch transaction as invalid

How to test

[github-actions]

k6 load testing comparison.
Base Commit Hash: 8135bf8
Target Commit Hash: 4f5e8c1

Metric	Base				Target				Diff
	Avg	Max	90	95	Avg	Max	90	95	Avg	Max	90	95
Blocks	62.22	1454.19	63.05	65.41	58.57	1244.90	60.20	63.33	-5.86% ✅	-14.39% ✅	-4.51% ✅	-3.17% ✅
Accounts	54.56	862.28	62.67	64.01	51.98	363.44	59.62	61.09	-4.73% ✅	-57.85% ✅	-4.86% ✅	-4.55% ✅
Mex	53.76	830.11	62.62	63.92	51.78	775.96	59.63	61.09	-3.68% ✅	-6.52% ✅	-4.77% ✅	-4.44% ✅
Nodes	53.90	751.54	62.61	63.95	51.56	121.25	59.68	61.08	-4.35% ✅	-83.87% ✅	-4.68% ✅	-4.48% ✅
Pool	54.05	539.47	62.63	63.94	52.45	789.62	59.66	61.11	-2.96% ✅	+46.37% 🔴	-4.74% ✅	-4.43% ✅
Transactions	87.85	3207.61	63.57	66.26	81.02	2646.06	60.42	64.84	-7.77% ✅	-17.51% ✅	-4.96% ✅	-2.14% ✅
Tokens	54.27	669.04	62.65	63.93	52.45	702.56	59.64	61.19	-3.36% ✅	+5.01% 🔴	-4.79% ✅	-4.30% ✅
Test Run Duration	60002.32				60005.86

Legend: Avg - Average Response Time, Max - Maximum Response Time, 90 - 90th Percentile, 95 - 95th Percentile
All times are in milliseconds.