[lldb][Progress] Separate title and details (#77547)

Per this RFC:
https://discourse.llvm.org/t/rfc-improve-lldb-progress-reporting/75717
on improving progress reports, this commit separates the title field and
details field so that the title specifies the category that the progress
report falls under. The details field is added as a part of the
constructor for progress reports and by default is an empty string. In addition, changes the total amount of progress completed into a std::optional. Also
updates the test to check for details being correctly reported from the
event structured data dictionary.