worker: define Symbol.toStringTag on messaging prototypes

[santusht06]

Per the HTML and WebIDL specifications, interface prototypes must define @@toStringTag (Symbol.toStringTag) with the interface name as a configurable, non-writable, non-enumerable property.

In Node.js, MessageChannel, MessagePort, and BroadcastChannel prototypes lacked explicit Symbol.toStringTag definitions. This resulted in incorrect string representations:

• Object.prototype.toString.call(new MessageChannel()) returned [object Object]
• Object.prototype.toString.call(new MessageChannel().port1) returned [object EventTarget] (inherited from EventTarget.prototype)
• Object.prototype.toString.call(new BroadcastChannel('foo')) returned [object EventTarget]

Changes

• Defined [SymbolToStringTag] on MessagePort.prototype with { configurable: true, value: 'MessagePort' }.
• Defined [SymbolToStringTag] on MessageChannel.prototype with { configurable: true, value: 'MessageChannel' }.
• Defined [SymbolToStringTag] on BroadcastChannel.prototype with { configurable: true, value: 'BroadcastChannel' }.
• Added test/parallel/test-worker-messaging-string-tag.js to test prototype property descriptors and toString tags for instances and globals.
• Updated test/parallel/test-worker-message-port-inspect-during-init-hook.js and test/parallel/test-eventtarget-memoryleakwarning.js to reflect that inspect / warning output now formats as MessagePort instead of MessagePort [EventTarget].

Fixes: #65527

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.13%. Comparing base (54b4e37) to head (7e54b9a).
⚠️ Report is 251 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #65531   +/-   ##
=======================================
  Coverage   90.13%   90.13%           
=======================================
  Files         751      751           
  Lines      253635   253654   +19     
  Branches    47786    47798   +12     
=======================================
+ Hits       228615   228642   +27     
+ Misses      16268    16265    -3     
+ Partials     8752     8747    -5     

Files with missing lines	Coverage Δ
lib/internal/worker/io.js	99.22% <100.00%> (+0.02%)	⬆️

... and 21 files with indirect coverage changes

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[santusht06]

Closing to focus on one PR at a time as per contributor guidelines. Will revisit after #65580 is merged.