Add Missing Dash Roles to RoleFromString function

[Johmpa]

System info

Operating System: macOS 14.5
Shaka Packager Version: 3.2.0

Issue and steps to reproduce the problem

As issue #1390 identified, several Dash roles in the specification were missing. These were added and included in the 3.1.0 release.

However, many of the possible roles are not present in the RoleFromString function in period.cc, resulting in a failed packaging since the roles cannot be recognized.

The following roles appear to be missing from the function:

• karaoke
• sign
• metadata
• enhanced-audio-intelligibility
• emergency
• easyreader

Packager Command:

~/Movies/videodev/packager-test/source/shaka-packager/build/packager/packager \
in=avc1080.mp4,stream=audio,output=audio.mp4,playlist_name=audio.m3u8,hls_group_id=audio,hls_name=ENGLISH,dash_roles=karaoke \
 in=avc1080.mp4,stream=video,output=avc.mp4,playlist_name=avc.m3u8,iframe_playlist_name=avc_iframe.m3u8 \
 --hls_master_playlist_output main.m3u8 \
 --mpd_output main.mpd

What is the expected result?
A successful packaging with the role "Karaoke" assigned.

What happens instead?
code: 139, [0813/160352:ERROR:period.cc(208)] Unrecognized role 'karaoke'