add callback to allow level change in debugger

[KedoKudo]

The current debugger widget does not update the logging level once it is instantiated.
For example, the console created with the following code will always have its logging level set at given value:

import panel as pn
import param
import logging

pn.extension('terminal')

console = pn.widgets.Debugger(
            name="Console",
            level=logging.INFO,
            sizing_mode="stretch_width",
            logger_names=["panel", "imars3d"],
        )

console.level = logging.DEBUG   # <- this does not have any impact on the console widget due to missing callbacks

This PR adds a callback function that retrieve the stream and set the new log level for all tracking loggers.

[codecov]

Codecov Report

Merging #4057 (830c1b4) into master (1647fa3) will decrease coverage by 0.11%.
The diff coverage is 80.00%.

@@            Coverage Diff             @@
##           master    #4057      +/-   ##
==========================================
- Coverage   83.53%   83.42%   -0.12%     
==========================================
  Files         223      223              
  Lines       33219    33223       +4     
==========================================
- Hits        27751    27715      -36     
- Misses       5468     5508      +40     

Flag	Coverage Δ
ui-tests	37.58% <60.00%> (+0.01%)	⬆️
unitexamples-tests	74.09% <75.00%> (-0.48%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
panel/widgets/debugger.py	92.42% <80.00%> (-0.55%)	⬇️
panel/models/quill.py	71.42% <0.00%> (-14.29%)	⬇️
panel/tests/pane/test_base.py	84.00% <0.00%> (-12.00%)	⬇️
panel/models/echarts.py	76.47% <0.00%> (-11.77%)	⬇️
panel/models/terminal.py	81.25% <0.00%> (-9.38%)	⬇️
panel/models/jsoneditor.py	75.00% <0.00%> (-9.38%)	⬇️
panel/tests/template/test_vanilla_manual.py	78.26% <0.00%> (-8.70%)	⬇️
panel/models/ace.py	83.33% <0.00%> (-8.34%)	⬇️
panel/tests/template/test_manual.py	57.57% <0.00%> (-4.05%)	⬇️
panel/tests/widgets/test_speech_to_text.py	88.65% <0.00%> (-2.07%)	⬇️
... and 10 more

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[philippjfr]

Looks good, thank you!

[philippjfr]

Test failures are unrelated. Merging.