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