Add FF_COUNTERFACTUAL_BALANCES

[hectorgomezv]

Summary

Counterfactual balances are being retrieved when the Safe doesn't exist (it is not known by the Safe Transaction Service). This PR set that as an optional behavior, so the existence of a Safe and the use of an alternative source for the balances associated can be (de)activated via this FF.

Changes

• Adds FF_COUNTERFACTUAL_BALANCES feature flag.

[coveralls]

Pull Request Test Coverage Report for Build 9447473695

Details

• 8 of 8 (100.0%) changed or added relevant lines in 1 file are covered.
• 4 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.02%) to 92.717%

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Files with Coverage Reduction	New Missed Lines	%
src/datasources/balances-api/zerion-balances-api.service.ts	4	81.9%

Totals
Change from base Build 9444680700:	0.02%
Covered Lines:	7127
Relevant Lines:	7388

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9447499865

Details

• 8 of 8 (100.0%) changed or added relevant lines in 1 file are covered.
• 4 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.003%) to 92.697%

---

Files with Coverage Reduction	New Missed Lines	%
src/datasources/balances-api/zerion-balances-api.service.ts	4	81.9%

Totals
Change from base Build 9444680700:	-0.003%
Covered Lines:	7128
Relevant Lines:	7388

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💛 - Coveralls