Add Dashboard Navigation block to Navigation sidebar on update

Problem/Motivation

Follow up issue after #3563965: Switch from custom Varbase Dashboard icon to the Dashboard block icon, which was messing
When upgrading Varbase or enabling the Dashboard and Navigation modules, the Dashboard Navigation block is not automatically added to the Navigation sidebar layout.

This results in:

• The Dashboard feature being enabled
• But no visible Dashboard entry in the Navigation sidebar
• Manual intervention required to place the block

This causes an inconsistent admin experience and breaks the expected default behavior.

Proposed resolution

• Checks that both navigation and dashboard modules are enabled
• Loads the navigation.block_layout configuration
• Verifies that the navigation_dashboard block is not already present
• Automatically adds the Dashboard Navigation block to the Navigation sidebar layout
• Ensures the update is safe, idempotent, and does not duplicate blocks

An update hook which adds the navigation_dashboard block to the Navigation layout only when missing, using a generated UUID and preserving existing layout sections.

Remaining tasks

• ✅ File an issue about this project
• ✅ Addition/Change/Update/Fix to this project
• ✅ Testing to ensure no regression
• ➖ Automated unit/functional testing coverage
• ➖ Developer Documentation support on feature change/addition
• ➖ User Guide Documentation support on feature change/addition
• ➖ UX/UI designer responsibilities
• ➖ Accessibility and Readability
• ✅ Code review from 1 Varbase core team member
• ✅ Full testing and approval
• ✅ Credit contributors
• ✅ Review with the product owner
• ✅ Update Release Notes and Update Helper on new feature change/addition
• ❌ Release varbase-10.1.1, varbase_dashboards-2.0.1

Varbase update type

• ✅ No Update
• ➖ Optional Update
• ➖ Forced Update
• ➖ Forced Update if Unchanged

User interface changes

After the fix:
when we run drush updb

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• fix: #3566085 Add Dashboard Navigation block to Navigation sidebar on update