[run_test_suite] Allow the ansi filter to be chained

Updates the ansi filter so that it takes a WriteLine implementator
rather than a Write implementor. This allows chaining together
different WriteLine implementors.

Change-Id: I8670f6bb29ed49b01a4e121d6be94df69a6aed92
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/513991
Reviewed-by: Ankur Mittal <anmittal@google.com>
Reviewed-by: Christopher Johnson <crjohns@google.com>
Commit-Queue: Satsuki Ueno <satsukiu@google.com>