Chore: skip test files in coverage, use SafeL2 contract for coverage calculation

[mmv08]

This PR:

• Skips test files that were introduced during work on 1.4.1 and 1.5.0 and negatively affected test coverage
• Includes the environment variable used for Safe Contract instance under testing to the sample env file
• Use SafeL2 contract for the coverage test

[coveralls]

Pull Request Test Coverage Report for Build 6458179212

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+2.3%) to 95.177%

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Totals
Change from base Build 6456165180:	2.3%
Covered Lines:	367
Relevant Lines:	376

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💛 - Coveralls