The skipIfOutOfTreeDebugserver decorator is meant to skip tests that exercise functionalities that may not be present yet in a debugserver that ships with Xcode. This is inherently tied to a version of debugserver and therefore a version should be part of the decorator. This patch extends the decorator to take an operator and a debugserver version.
This patch also removes the --out-of-tree-debugserver dotest flag. Instead we expect --server to be passed even when using a system debugserver, which is used to deduct the current version.