improve progress reporting

* use erase rest of line escape code.
 * use `stderr.supportsAnsiEscapeCodes` rather than `isTty`.
 * respect `--color off`
 * avoid unnecessary recursion
 * add `Progress.log`
 * disable the progress std lib test since it's noisy and uses
   `time.sleep()`.
 * enable/integrate progress printing with the default test runner

src/userland.cpp

@@ -87,3 +87,4 @@ Stage2ProgressNode *stage2_progress_start(Stage2ProgressNode *node,
 }
 void stage2_progress_end(Stage2ProgressNode *node) {}
 void stage2_progress_complete_one(Stage2ProgressNode *node) {}
+void stage2_progress_disable_tty(Stage2Progress *progress) {}