ListOption currently uses llvm:🆑:list under the hood, but the usages
of ListOption are generally a tad different from llvm:🆑:list. This
commit codifies this by making ListOption implicitly comma separated,
and removes the explicit flag set for all of the current list options.
The new parsing for comma separation of ListOption also adds in support
for skipping over delimited sub-ranges (i.e. {}, [], (), "", ''). This
more easily supports nested options that use those as part of the
format, and this constraint (balanced delimiters) is already codified
in the syntax of pass pipelines.
See https://discourse.llvm.org/t/list-of-lists-pass-option/5950 for
related discussion
Differential Revision: https://reviews.llvm.org/D122879
6edef13569