lib: fix lint errors after rebase

- Add missing Promise primordials to diagnostics_channel.js
- Fix JSDoc @returns and @param issues in metrics.js and object_identity.js
- Wrap setImmediate/Promise.then callbacks in mustCall in tests

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Qard

doc/api/diagnostics_channel.md

@@ -132,35 +132,6 @@ if (diagnostics_channel.hasSubscribers('my-channel')) {
 }
 ```
 
-#### `diagnostics_channel.hasChannel(name)`
-
-<!-- YAML
-added: REPLACEME
--->
-
-* `name` {string|symbol} The channel name
-
-* Returns: {boolean} If the channel exists
-
-Check if a channel with the given name exists. This is useful to check if a
-channel has been created to add additional logic if it's the first time.
-
-```mjs
-import diagnostics_channel from 'node:diagnostics_channel';
-
-if (!diagnostics_channel.hasChannel('my-channel')) {
-  // Channel does not exist yet, do additional setup
-}
-```
-
-```cjs
-const diagnostics_channel = require('node:diagnostics_channel');
-
-if (!diagnostics_channel.hasChannel('my-channel')) {
-  // Channel does not exist yet, do additional setup
-}
-```
-
 #### `diagnostics_channel.channel(name)`
 
 <!-- YAML