[lldb/Core] Fix finite progress event reporting

This patch should fix event handling for finite progress reports.

Previously, the event handler would get stuck when receiving a finite
progress report, and stop displaying upcoming reports.
This was due to the fact that we were checking if the progress event was
completed by calling `GetCompleted` but returns the completion amount
instead of saying whether it's completed.

That caused the current event id to remain the same, preventing all the
following progress reports to be shown to the user.

This patch also adds some logging to facilitate debugging progress events.

rdar://91788326

Differential Revision: https://reviews.llvm.org/D128768



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