feat(pip): add debug logging for better PiP flow observability

[hristoterezov]

Summary

• Add logger.debug calls in modules/API/API.js when dispatching _pip-requested, pip-entered, and pip-left events to the External API
• Add state-aware debug logs in react/features/pip/actions.ts for showPiP, hidePiP, exitPiP, handleWindowBlur, and handleWindowFocus — each log includes the relevant PiP state snapshot
• Add logger.debug (and a .then() success branch) to requestPictureInPicture() in react/features/pip/functions.ts to capture both success and failure of the native API call
• Add logger import and debug logs in react/features/pip/subscriber.ts when the Electron namespace is mutated to expose/remove requestPictureInPicture

Motivation

Debugging PiP behaviour in production and staging environments required attaching a debugger or adding temporary print statements. These structured debug logs make the full PiP lifecycle visible through the existing logging infrastructure without changing any functional behaviour.

Test plan

• Join a meeting and trigger PiP (e.g. switch away from the window in Electron or call showPiP)
• Verify debug-level log messages appear for each PiP event in the browser/Electron console
• Confirm no regressions in PiP enter/exit flow in both browser and Electron contexts