[lldb] Don't report progress in the REPL

Don't report progress events in the REPL. Most of the progress events
are debugger specific which are useful when you're debugging, but not so
much when you're waiting for the next line to be executed in the REPL.

This patch disables reporting of progress events when in REPL mode.

rdar://91502950

Differential revision: https://reviews.llvm.org/D123426