Add Moderation API and stable response types

[winrid]

Moderation API

Adds a Moderation API with methods for the moderator dashboard:

• Comments — list, count, fetch by id(s) and children, get/set comment text, logs, export, search (users / pages / sites / comments), suggestions
• Moderation actions — remove / restore, flag / un-flag, set review / spam / approval status, adjust / cast / delete votes, reopen / close thread
• Bans — ban from comment, undo ban, pre-ban and bulk pre-ban summaries, comment ban status, ban preferences, banned-user counts and lookup
• Badges & trust — award / remove badge, manual badges, get / set trust factor, user internal profile

All Moderation methods accept an sso parameter for SSO-authenticated moderators.

Response types (breaking)

Each method now returns its success response type directly, with errors surfaced as a default error response, instead of the previous combined success-or-error return type. The response type names are now stable. Response shapes are unchanged.

Recommend a major version bump.