Add tests for CommonForEachStatementSyntaxWrapper

[sharwell]

This wrapper type was added in #2370 without tests. It's not too difficult to add them; see commit c31beae and other examples from that pull request for how to implement good coverage of these types.

📝 Make sure to test that ForEachStatementSyntax can be cast to this wrapper type with full functionality in Roslyn 1.x.

[bjornhellander]

Has this already been handled completely in commit e57e1b3? There is at least a CommonForEachStatementSyntaxWrapperTests class.