009dd1cc

By: Tom Sydney Kerckhove <syd@cs-syd.eu>

Code review fixes: --out-dir, doc clarifications, forgivingAbsence

* Make --out-dir required for the run subcommand.  The help text used
  to say "defaults to CWD" but Nothing actually skipped writing report
  files altogether — a confusing two-meanings overload that
  disappears now that the setting is required.
* Rename "wall-clock" to "monotonic-clock" in doc comments and
  identifier names where the underlying timing is getMonotonicTimeNSec
  (which has been the implementation for a while now).
* Move the AugmentedManifestDecodeException type so the haddock on
  readAugmentedManifestFile attaches to it rather than to the exception.
* readAugmentedManifestFileIfExists now uses forgivingAbsence instead
  of doesFileExist + read (closes a TOCTOU window and matches the rest
  of the codebase).
* listSuiteTestIds names the offending line(s) when it fails to parse.