[System.Web] Remove superfluous write to file in test

The written file is never used, all the Asserts happen in RenderPostBackEvent_OnSaveStateComplete ().
[MWF] Get rid of unused resx.resx file

The other tests already use GetResXFileWithNode () to create this file, make this consistent and get rid of the checked-in file
[System.IO.Compression] Delete test file after test
[System.Drawing] Delete test files after test
[mdoc] Ignore generated test files
Merge pull request #1147 from akoeplinger/misc-test-cleanup

Cleanup untracked test files