Simplified clear screen command

[hugsy]

Description

Add a new GEF config item

───────────────────────────────────── GEF configuration setting: gef.clear_screen_command ─────────────────────────────────────
gef.clear_screen_command (str) = "clear -x"

Description:
        Command to use to clear the screen.

Fixes #1147

Checklist

• My code follows the code style of this project.
• My change includes a change to the documentation, if required.
• If my change adds new code, adequate tests have been added.
• I have read and agree to the CONTRIBUTING document.

[github-actions]

🤖 Coverage update for 82ae86c 🟢

	Old	New
Commit	5376d78	82ae86c
Score	71.2662%	71.2717% (0.0055)

[github-actions]

🤖 Coverage update for 82ae86c 🟢

	Old	New
Commit	5376d78	82ae86c
Score	71.2662%	71.2662% (0)

[hugsy]

bad idea

[github-actions]

🤖 Coverage update for a9930ea 🟢

	Old	New
Commit	5376d78	a9930ea
Score	71.2662%	71.3369% (0.0707)

[github-actions]

🤖 Coverage update for a9930ea 🟢

	Old	New
Commit	5376d78	a9930ea
Score	71.2662%	71.2662% (0)

[ValekoZ]

LGTM, maybe some code can be removed, that's up to you if you think it is still useful we can keep it here

[github-actions]

🤖 Coverage update for 730e418 🟢

	Old	New
Commit	5376d78	730e418
Score	71.2662%	71.3105% (0.0443)

[github-actions]

🤖 Coverage update for 730e418 🟢

	Old	New
Commit	5376d78	730e418
Score	71.2662%	71.2662% (0)