Use native browser for help - rebased against current main

[rozyczko]

Description

This is a preliminary version of the QtWebEngine-less SasView rebased against current main.
Original PR: #3847
All calls have been converted to consistent system browser calls.
References to QtWebEngine were removed.
Tests updated (although we don't run these tests, anyway)

Fixes #3511

How Has This Been Tested?

Locally win11

Review Checklist:

[if using the editor, use [x] in place of [ ] to check a box]

Documentation (check at least one)

• There is nothing that needs documenting
• Documentation changes are in this PR
• There is an issue open for the documentation (link?)

Installers

• There is a chance this will affect the installers, if so
  • Windows installer (GH artifact) has been tested (installed and worked)
  • MacOSX installer (GH artifact) has been tested (installed and worked)
  • Wheels installer (GH artifact) has been tested (installed and worked)

Licensing (untick if necessary)

• The introduced changes comply with SasView license (BSD 3-Clause)

[krzywon]

I'm approving this and will merge it before our biweekly call next week.

There is one minor thing that can either be fixed here, or that I'll create an issue for after merging. https://www.sasview.org/docs/v6.1.2/ which is opened during unit tests, doesn't exist but does resolves as a 404 page. Older documentation is found in https://www.sasview.org/docs/old_docs/X.Y.Z/. In the future, if we move to a different web server system, the URL might not resolve, and would break the unit test.