Event data should generally not be mutate as any mutations can leak to other listeners. This change marks most event type members as readonly

## Problem
The diagnostic collection object is set up so that it does not mutate the arrays of diagnostics you pass to it. It also does not expect or allow mutation of diagnostics that it returns.

However it it currently typed using normal arrays. This means that if an extension (such as JS/TS) wishes to use readonly diagnostics intnernally, it cannot do so without casting.

## Proposed Fix
Use `ReadonlyArray` in diagnostic collection. This should be a safe change for the `set` type methods. The changes to `get` and `forEach` have the risk of breaking the typing of some extensions, but `get` already returned a frozen array of diagnostic so trying to mutate the array itself would have resulted in runtime error.

* Rename user to author for Comment.

* Make Comment interface

* Fix #73170. Introduce CommentAuthorInformation

* Fix #73145. Update range properly.

* Comments API Finalization

Fixes #72152

* Expose uri scheme through vscode.env

Thenble -> Thenable

Part of #70716

Issue #8429 has been fixed a long time ago.

Fixes #70716
Fixes #70713

- Priority can be undefined. Update public api to match this
- We also use an undefined `extensionId`. Update typings for this