Better experimental_create_proxy

[WebReflection]

This MR would like to improve the story around experimental_create_proxy flag:

• both callbacks and dictionaries or any other Pythonic reference are converted into JS
• the FinalizationRegistry is already integrated in Pyodide, no need to duplicate that effort
• smaller code and more reliable, also tested with a real-world use case (see test folder)
• removed the patch for main only, once the flag is enabled, it patches workers too regardless

This should simplify by far code sharing between MicroPython and Pyodide avoiding redundant, unexpected, sometimes wrongly handled explicit to_js and create_proxy calls ... it's all automatically handled by the JS GC