Add possibility to filter coverage files which should be reported to Codecov

[pascalberger]

Codecov uploads when total size of coverage files is bigger than 20 MB. Cake.Recipe always uploads all coverage reports. If tests run against multiple .NET 8 versions, coverage for every version is uploaded and can lead to the upload limit being reached. In this case it would be helpful to have the possibility to define a filter which is applied when the coverage files are determined.