Migrate core logic of deletecontent and exportcontent to a util function

[thesujai]

Summary

This refactors the exportcontent and exportcontent commands and its related tasks

• Moved the exportcontent core logic to export_content util function
• Updated the diskexport task to use export_content instead of calling exportcontent command
• Moved the deletecontent core logic to delete_content util function
• Updated deletechannel task to user delete_content

References

Fixes #13209
Fixes #13208

Reviewer guidance

• Try soft delete and force delete a content
• Export a channel contents to a file

[github-actions]

Build Artifacts

Asset type	Download link
PEX file	kolibri-0.18.0b1.dev0_git.7.gd244a165.pex
Windows Installer (EXE)	kolibri-0.18.0b1.dev0+git.7.gd244a165-windows-setup-unsigned.exe
Debian Package	kolibri_0.18.0b1.dev0+git.7.gd244a165-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.18.0b1.dev0+git.7.gd244a165.dmg
Android Package (APK)	kolibri-0.18.0b1.dev0+git.7.gd244a165-0.1.4-debug.apk
Raspberry Pi Image	kolibri-pi-image-0.18.0b1.dev0+git.7.gd244a165.zip
TAR file	kolibri-0.18.0b1.dev0+git.7.gd244a165.tar.gz
WHL file	kolibri-0.18.0b1.dev0+git.7.gd244a165-py2.py3-none-any.whl

[thesujai]

Hi @rtibbles, marking this as ready for review

[MisRob]

Thanks @thesujai! We will review in the upcoming weeks. I wanted to note that review waiting times are still longer.