Add zkSync support to `SafeToL2Migration` tests

[mmv08]

This PR:

• Almost Implements #767 by applying the same principles to SafeToL2Migration tests as in https://github.com/safe-global/safe-smart-account/pull/833
• I will cherry-pick the changes back to 1.4.1 branch once the hardhat compiler plugin issue is addressed

[coveralls]

Pull Request Test Coverage Report for Build 10946754749

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 93.571%

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Totals
Change from base Build 10945831503:	0.0%
Covered Lines:	396
Relevant Lines:	408

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💛 - Coveralls