feat: multi-window support (#109)

* Init window after event loop inited

* Fix typo

* Fix resize event

* Return boolean after resize

* Update verso to hold hashmap of windows

* Improve shutdown logic

* Fix scale factor on Linux

* Present directly after composite

* Add some fields to prepare for multisurface

* Add initial multi-surface support

* Add document ID field in window

* Update to latest servo

* Create correct window spawning order

* Create separate display list for different surface

* Fix flashing

* Improve set_painting_order safety

* Improve webview creation flow

* Update unsupported log to trace

* Fix resize and add more debug logs

* Remove unecessary step

* Address review changes

* Update compositor document

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Co-authored-by: Wu Yuwei <Wu Yu Wei>

Author: wusyong