sig#855 - Upgrade app dependencies

[evegufy]

As part of the regular maintenance the dependencies need to be upgraded.

TODO's:

• upgrade dependencies - use existing dependabot PRs where possible, upgrade xunit* dependencies manually due to dependabot limitation - and solve possible issues which araise from the upgrade
• open IP review requests at the Eclipse Foundations GitLab for this dependencies which the Dash Tool signals accordingly
• monitor IP review requests and answer questions if needed
• update DEPENDENCIES file once all IP review requests have been approved

GH actions and docker are out of scope for this issue

xunit*:
xunit
xunit.runner.visualstudio
Xunit.Extensions.AssemblyFixture