Unify browser test files and add safari tests (#88)

* refactor: Update crepto_subtle_test

* feat: Add safari test

* refactor: Focus on the type of error

* fix: Fix firefox test

* Update test/crypto_subtle_test.dart

Co-authored-by: Jonas Finnemann Jensen <[email protected]>

* refactor: Cleanup

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Co-authored-by: Jonas Finnemann Jensen <[email protected]>

Author: koji-1009