Review Process

- Update constructor and `Process::withShellCommand()` parameters
- Replace `null` input with an empty stream (`STDIN` must now be passed
  explicitly via `Process:pipeInput()`)
- Improve robustness and precision of timeout handling and process
  termination
- Add setter methods `setCwd()`, `setEnv()`, `setTimeout
  ()`, `disableOutputCollection()`, `enableOutputCollection()`
- Add `Process::isTerminatedBySignal()`
- In `Process::runWithoutFail()`, throw `ProcessFailedException` when a
  process returns a non-zero exit status
- Throw `ProcessTerminatedBySignalException` when a process monitored by
  `Process::wait()` is terminated by a signal that isn't a `SIGTERM` or
  `SIGKILL` sent after calling `Process::stop()`
- Throw `LogicException` instead of `ProcessException` where
  appropriate
- Add `Process::getStats()` metrics
- Fix output collection bugs
- Update tests

Author: lkrms

src/Toolkit/Core/Exception/ProcessFailedException.php

@@ -0,0 +1,8 @@
+<?php declare(strict_types=1);
+
+namespace Salient\Core\Exception;
+
+/**
+ * @api
+ */
+class ProcessFailedException extends ProcessException {}

src/Toolkit/Core/Exception/ProcessTerminatedBySignalException.php

@@ -0,0 +1,8 @@
+<?php declare(strict_types=1);
+
+namespace Salient\Core\Exception;
+
+/**
+ * @api
+ */
+class ProcessTerminatedBySignalException extends ProcessException {}