[DwarfDump] Add new set of line-table-related statistics to llvm-dwarfdump (#93289)

This patch adds a new set of statistics to llvm-dwarfdump that provide
additional information about .debug_line regarding the number of bytes
covered by the line table (and how many of those are covered by line 0
entries), and the number of entries within the table and how many of
those are is_stmt, unique, or unique and non-line-0 (where "uniqueness"
is based on file, line, and column only).

Collectively these give a little more insight into the state of debug
line information, rather than variables (as most of the dwarfdump
statistics are currently oriented towards). I've added all of the stats
that were useful to some degree, but I think the most generally useful
stat is "unique line entries", since it gives the most straightforward
indication of regressions, i.e. when the number goes down it means that
fewer source lines are reachable in the program.