Olympia mappings - runtime forum/proposals changes adjustments, support for forum tags and proposals discussion

[Lezek123]

Includes merged and updated work from #2436 (proposals discussion mappings) and adjustments related to changes introduced in:

• Forum: Expose initial post_id in ThreadCreated event #2527 - PostId is now retriveable from ThreadCreated event data
• Olympia forum: create_thread extrinsic should take poll description, not description_hash, as arg #2531 - PollInput type was introduced, which fixes the issue related to forum poll input data
• Forum thread tags (runtime part) #2537 - ThreadTitle -> ThreadMetadata runtime renaming for consistency due to the introduction of ForumThread metadata in order tu support forum tags (Olympia: Support for forum thread labels/tags #2422)
• Proposals: cleaun-up ProposalCreated event #2539 - ProposalId was incuded as part of proposalCodex.ProposalCreated event and proposalEngine.ProposalCreated event was removed, unifying the source of new proposal data and allowing to remove the temporary workaround with cached proposal id.

Notable changes:

• Forum tags are now supported as desribed in Olympia: Support for forum thread labels/tags #2422. create_thread extrinsic and edit_thread_metadata (previously edit_thread_title) now take encoded ForumMetadata as argument. The ThreadTitleUpdatedEvent entity has been renamed to ThreadMetadataUpdatedEvent
• ForumTag.visibleThreadsCount and ForumThread.visiblePostsCount fields have been added, which will faciliate querying forum threads / tags by popularity (required by Pioneer 2). visible means that the posts/threads beeing counted are either Active or Locked, so this excludes posts/thread that are (or in case of post - are part of a thread that is) Moderated or Removed.
• Initial post in the thread will now have a valid ID
• The input format for polls in create_thread has been changed to take the actual input data instead of hashes.
• delete_posts extrinsic signature has been changed. The extrinsic now takes BTreeMap as argument, which may require updating to @polkadot/api 5.2.1 (see: BTreeSet and BTreeMap - encoding and serialization fixes polkadot-js/api#3789) (this update was already done on this branch)

[jodator]

@Lezek123 & @mnaamani It looks that most of the queries now work with Olympia testnet 🎉

We do have however two minor issues regarding querying Hydra:

1. Apply role filters for member search pioneer#857 (comment)
2. Active posts queries do not work with Olympia testnet pioneer#1431

[jodator]

As in the comment above ☝️ Most of the things in the Pioneer app works properly with the Olympia testnet.

[ondratra]

We do have however two minor issues regarding querying Hydra:

1. Apply role filters for member search pioneer#857 (comment)

This issue is being solved in Hydra PR Joystream/hydra#453 and tracked in ticket Joystream/hydra#444 . So I think we can merge this PR and solve the said problem separately.