[FEATURE][Python console] Run shell commands from the console

[YoannQDQ]

Description

Mimics IPython behavior to run system command from the Python console.

• Run any command that works at the command-line with the syntax !cmd. The console will start a subprocess, and forward its output to the Python Console Output.
• While the subprocess is running, the Python Console Input switch to STDIN mode and forwards entered character to the child process. This make it possible to send confirmation when the child program ask for it.
• EASY pip install/remove !!!
• When the Console is in STDIN mode, pressing Ctrl+C kills the subprocess.
• Affect the result of a command to a variable with the syntax var = !cmd

Example

>>> !echo Hello
Hello

>>> !gdalinfo --version
GDAL 3.4.1, released 2021/12/27

>>> sql_formats = !ogrinfo --formats | grep SQL
>>> sql_formats
['SQLite -vector- (rw+v): SQLite / Spatialite', '  MSSQLSpatial -vector- (rw+): Microsoft SQL Server Spatial Database', '  PostgreSQL -vector- (rw+): PostgreSQL/PostGIS', '  MySQL -vector- (rw+): MySQL', '  PGDUMP -vector- (w+v): PostgreSQL SQL dump']

[github-actions]

@YoannQDQ
This pull request has been tagged as requiring documentation.

A documentation ticket will be opened at https://github.com/qgis/QGIS-Documentation when this PR is merged.

Please update the description (not the comments) with helpful description and screenshot to help the work from documentors.
Also, any commit having [needs-doc] or [Needs Documentation] in will see its message pushed to the issue, so please be as verbose as you can.

Thank you!

[nirvn]

@YoannQDQ , really nice feature.

[YoannQDQ]

@nyalldawson Would you care to review this? I'd really like to see it merged.

[m-kuhn]

I am in favor of merging this. It's a lot of system specific code in areas I don't know very well. But this is isolated to when the new functionality is actually used and so it should be save to send this for a wider test ride and react on feedback from different system.

[github-actions]

@YoannQDQ
A documentation ticket has been opened at qgis/QGIS-Documentation#8207
It is your responsibility to visit this ticket and add as much detail as possible for the documentation team to correctly document this change.
Thank you!