BrowserLauncher: Replace a function for appending additional arguments

This CL introduces `CommandLine::FromArgvWithoutProgram` in order to
make code simpler.

Involved with this change, `AppendAurguments` was removed.

Bug: 1513045
Change-Id: I7e6d085f747eb34c7cc6dfab4c3c8e9885e6ea80
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5192312
Reviewed-by: Eriko Kurimoto <elkurin@chromium.org>
Commit-Queue: Mayuko Aiba <mayukoaiba@google.com>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1246406}