Drools 8 docs : throughout review. Fix broken links, outdated description

After adding most of missing parts (= other Drools 8 docs JIRAs), let's fully review to check if there are any defects or outdated things.

Issue Description: <{}This is the problem you are trying to solve. Please use instructions of how to recreate the issue and screenshots to help>{}

Review the entire documents to check if there are any defects or outdated things. Then fix/update them if exist.

Acceptance Criteria: <Use this section to define the definition of done for this issue>

• Drools 8 docs don't contain broken links, outdated features/components

Out of Scope: <Here you need to fill in what is out of scope for this issue and then create new issues if necessary in the backlog for the work>

N/A

Additional Information: <Add any additional information here that may be helpful to people reading the ticket>

N/A