We can get repeated positions from optimized code objects in some cases
but for our purposes of looking up a line number from a PC, we can only
return one line number so just use the first one that is reported in
the source position table on the code object.

Change-Id: I4c0e866fb1948f65bf6c988d992ef55f520dd874
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1724375Reviewed-by: Alexei Filippov <alph@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62972}