[Release] Update contributors list format and sort it

Additionally, we now warn the user when a duplicate author name
arises, in which case he/she needs to resolve it manually.

Conflicts:
	.rat-excludes
[HOTFIX] Fix RAT exclusion for known_translations file

Author: Josh Rosen <joshrosen@databricks.com>

Closes #3719 from JoshRosen/rat-fix and squashes the following commits:

1542886 [Josh Rosen] [HOTFIX] Fix RAT exclusion for known_translations file

(cherry picked from commit 3d0c37b8118f6057a663f959321a79b8061132b6)
Signed-off-by: Josh Rosen <joshrosen@databricks.com>