Fix ipywidget Output widget bug

[giswqs]

Leafmap uses ipywidget's Output widget heavily to display text and plots. It appears that Output widget behaves different in different environments, causing issues such as disappearing maps in ArcGIS Pro.

The problematic way:

import ipywidgets as widgets
output = widgets.Output()
with output:
    print('Hello World')
output

output.clear_output()

The recommended way:

import ipywidgets as widgets
output = widgets.Output()
output.append_stdout('Hello World')
# output.append_display_data(data)
output

output.outputs = ()

Relevant issues:

• Output.clear_output() in a thread does not block until the output is cleared jupyter-widgets/ipywidgets#3260
• Output widget's clear_output not clearing when using append_stdout jupyter-widgets/ipywidgets#2584
• Allow Output.clear_output() to be thread-safe. jupyter-widgets/ipywidgets#3261
• ipywidgets Output widget not working properly widgetti/solara#127
• The geemap interactive map in ArcGIS Pro has some problems. gee-community/geemap#1578

[github-actions]

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