bump gtest to 1.13 and benchmarks to main head

[franziskuskiefer]

Update test and benchmark dependencies.

[coveralls]

Pull Request Test Coverage Report for Build 4730031599

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 53.441%

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Totals
Change from base Build 4730017181:	0.02%
Covered Lines:	30398
Relevant Lines:	56881

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💛 - Coveralls