docs: Added required steps for the Eclipse workspace

[salvatore-coppola]

Newest Eclipse versions include the plugin org.eclipse.m2e.pde.connector capable of handling the tycho packaging types in maven (e.g. eclipse-plugin, eclipse-feature, eclipse-test-plugin)

However we still need to use the old plugin org.sonatype.tycho.m2e because our old tycho version (1.7.0 for java 8).
So the need to include the plugin in the workspace and disable the m2e default lifecycle-mappings.

The change is automatically performed by the Oomph setup but I added the manual steps for users creating manually the workspace

[github-actions]

The backport to release-5.4.0 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-release-5.4.0 release-5.4.0
# Navigate to the new working tree
cd .worktrees/backport-release-5.4.0
# Create a new branch
git switch --create backport-5049-to-release-5.4.0
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 026be406771702e1a96be79dcce0f4926ac6d858
# Push it to GitHub
git push --set-upstream origin backport-5049-to-release-5.4.0
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-release-5.4.0

Then, create a pull request where the base branch is release-5.4.0 and the compare/head branch is backport-5049-to-release-5.4.0.