pw_console: Fix log pane rendering bugs

- For line wrapping: fix longest_channel_prefix_width calculation. Now
  reliably gets the length of the formatted log time and level.
- Console would hang at 100% cpu usage if the window width was less
  than longest_channel_prefix_width. That bug is fixed and test
  cases added.
- Change default log level to debug to not miss device log lines.

Bug: 401
No-Docs-Update-Reason: Bug fix.
Change-Id: I73f86ba71f5d91094d18f28491ca489059dfe961
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/50520
Commit-Queue: Anthony DiGirolamo <tonymd@google.com>
Reviewed-by: Joe Ethier <jethier@google.com>
diff --git a/pw_console/py/BUILD.gn b/pw_console/py/BUILD.gn
index 6542bca..ef1a54a 100644
--- a/pw_console/py/BUILD.gn
+++ b/pw_console/py/BUILD.gn
@@ -34,6 +34,7 @@
   tests = [
     "console_app_test.py",
     "help_window_test.py",
+    "helpers_test.py",
     "repl_pane_test.py",
   ]
   python_deps = [