Make SymbolFileDWARF::ParseLineTable use std::sort instead of insertion sort

Summary:
Motivation: When setting breakpoints in certain projects line sequences are frequently being inserted out of order.

Rather than inserting sequences one at a time into a sorted line table, store all the line sequences as we're building them up and sort and flatten afterwards.

Reviewers: jdoerfert, labath

Reviewed By: labath

Subscribers: teemperor, labath, mgrang, JDevlieghere, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D72909