Data viewer contribution should handle multiple entrypoints

[pwang347]

Based on offline chat with @rebornix @amunger, it would be good for the Jupyter extension to support handling of other launch points such as the Debug panel and anywhere else the existing viewer is shown. Thanks!

[amunger]

currently blocked on Data Wrangler's jupyterVariableViewers command contribution needing to handle cases with a debug session and no notebook.

[amunger]

verification steps:

1. Install Python, DataWrangler and Jupyter pre-release extensions
2. Create a .py file with the content below and set a breakpoint on the last print line
3. Debug the file (not in the Interactive Window)
4. When the breakpoint is hit, navigate to the variables view in the debug panel, right click df, and open the data viewer
5. Ensure Data Wrangler's data viewer is opened

import pandas as pd

# create a dictionary with sample data
data = {
    "name": ["Alice", "Bob", "Charlie", "David"],
    "age": [25, 30, 35, 40],
    "gender": ["F", "M", "M", "M"],
}

df = pd.DataFrame(data)

# print the dataframe
print(df)