chore: add language and translation flag to courseware api

[leangseu-edx]

Description

• add whole_course_translations_enabled flag and language fields to send to courseware api

Note:

• this pr should merge into feat: whole course translations waffle #34302
• the frontend pr course translation waffle flag frontend-app-learning#1305

[nsprenkle]

How would you feel about nesting these fields? I can see this becoming messy if we keep adding lots of one-off fields to this serializer.

course_settings: {
    course_language = "en",
    whole_course_translations_enabled = True / False,
    ....
}

[leangseu-edx]

How would you feel about nesting these fields? I can see this becoming messy if we keep adding lots of one-off fields to this serializer.

course_settings: {
    course_language = "en",
    whole_course_translations_enabled = True / False,
    ....
}

It is only 2 fields currently. I don't foresee it being more than this. It feel unnecessary.