[lldb] Add description to option completions.
Right now our argument completions are rather cryptic for command options as they only list the letters:
(lldb) breakpoint set - Available completions: -G -C -c -d -i -o -q -t -x [...]
With the new completion API we can easily extend this with the flag description so that it looks like this now:
(lldb) breakpoint set - Available completions: -G -- The breakpoint will auto-continue after running its commands. -C -- A command to run when the breakpoint is hit, can be provided more than once, the commands will get run in order left to right. -c -- The breakpoint stops only if this condition expression evaluates to true. -d -- Disable the breakpoint. -i -- Set the number of times this breakpoint is skipped before stopping. -o -- The breakpoint is deleted the first time it stop causes a stop. -q -- The breakpoint stops only for threads in the queue whose name is given by this argument. -t -- The breakpoint stops only for the thread whose TID matches this argument. -x -- The breakpoint stops only for the thread whose index matches this argument.
The same happens with --long-options now.
Reviewers: #lldb, labath
Reviewed By: labath
Subscribers: labath, JDevlieghere, lldb-commits
Differential Revision: https://reviews.llvm.org/D67063