Update Tx Service v2 API endpoints

[falvaradorodriguez]

• Updated API client with V2 endpoints added in this PR(Add V2 for multisigtransaction and all-transactions endpoints safe-transaction-service#2417) in the Tx Service.
• Minor fix when comparing safe_tx_hash to validate a transaction and the value of the safe_tx_hash is HexStr. The value of the attribute obtained when generating a SafeTx is HexBytes.
• Discarded the upgrade to V2 of the balances endpoint because for the moment there is no deprecation plan.

[coveralls]

Pull Request Test Coverage Report for Build 13901669081

Details

• 7 of 7 (100.0%) changed or added relevant lines in 3 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.04%) to 93.993%

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Files with Coverage Reduction	New Missed Lines	%
safe_eth/eth/tests/clients/test_etherscan_client_v2.py	1	87.5%

Totals
Change from base Build 13834119283:	0.04%
Covered Lines:	9514
Relevant Lines:	10122

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💛 - Coveralls