[lldb/Test] Add `use_colors` argument to the PExpect.launch wrapper

This patch adds a new `use_colors` argument to the PExpect.launch
method.

As the name suggests, it allows the user to conditionally enable color
support in the debugger, which can be helpful to test functionalities that
rely on that, like progress reporting. It defaults to False.

Differential Revision: https://reviews.llvm.org/D125915



Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>