tests: raise the default value for the various `devel.sync.*-timeout` configs These are used in `mercurial.testing.wait_file()` to stall for a file to appear in the filesystem, and raise an error if the file doesn't show up before the timeout expires. The default of 2s was way too low on Windows, especially when running tests in parallel, and resulted in various timeouts in `test-dirstate-read-race.t`, `test-dirstate-status-write-race.t`, and `test-clone-stream-revlog-split.t`. The various `wait-on-file` invocations in the tests are inconsistent, and wait anywhere from 5s - 20s. I'm using 20s here because if everything is working, the timeout won't matter. Also with the default timeout being raised on Windows in f4c038081561, both `HGTEST_TIMEOUT_DEFAULT` and `HGTEST_TIMEOUT` are 1440 in the default case where the timeout is not specified on the command line of the test runner, so the timing factor that is multipled with the value is 1, resulting in no changes. (But if someone specified a lower value on the command line, that would *lower* the timeout period used.)