Improve WebSocket error messages for CONNECTING state

[Nedunchezhiyan-M]

Summary

Replace opaque INVALID_STATE_ERR error messages in WebSocket's send() and ping() methods with descriptive messages that tell the developer what went wrong and which method was called. This matches the style used by browser WebSocket implementations.

Before: Error: INVALID_STATE_ERR
After: Error: Failed to execute 'send' on 'WebSocket': Still in CONNECTING state

Changelog:

[GENERAL] [CHANGED] - Improve WebSocket send() and ping() error messages when called in CONNECTING state

Test Plan

1. Create a WebSocket and immediately call send() before the connection opens
2. Verify the error message now reads "Failed to execute 'send' on 'WebSocket': Still in CONNECTING state"
3. Same for ping() - verify the descriptive message appears

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