Fix refreshable with function references

[falkoschindler]

This PR fixes #1283. It can be tested with the following example:

class Test:

    def __init__(self, name):
        self.name = name
        self.ui()

    @ui.refreshable
    def ui(self):
        ui.notify(f'Refreshing {self.name}')
        ui.button(self.name, on_click=self.ui.refresh)

Test('A')
Test('B')

Since the click handler holds a direct reference to the static refresh function, the instance isn't updated via __get__ when the button is clicked. Therefore this PR uses __getattribute__ to intercept when the refresh function is accessed while creating the button. It wraps refresh with the instance bound to the wrapper function. This way it always uses the right reference once the button is clicked.

[rodja]

Smart