Add a way to hide columns in the download table

[heldersepu]

This PR adds a simple way to hide columns in the download table

right clicking in the header header().customContextMenuRequested, will show a small menu in that menu we have options:

• allow the users to hide the clicked column header().hideSection(index)
• restore all hidden columns

[github-actions[bot]]

Hi @heldersepu, thank you for contributing to Tribler! 🚀

This PR was created by an outside collaborator, so some checks were not run for security reasons. To trigger the full set of checks, any member of the Tribler team can add the label PR: safe to check to the current PR.

[heldersepu]

@kozlovsky right-click context menu added

[heldersepu]

After you apply the fix, can you please squash all commits in the PR branch to make the commit history easier to read?

Fix applied, and all commits have been squashed