Import drools docs

[tkobayas]

• a part of Replace/Remove MPL 2.0 Licensed search-ui.js from drools-docs incubator-kie-issues#1710

This PR does:

• Copy incubator-kie-drools/drools-docs under incubator-kie-docs as drools-docs sub directory
• Move existing kogito docs from the root directory to kogito-docs sub directory

Once this PR is merged:

• We can remove drools-docs from incubator-kie-drools:main
• Need to update incubator-kie-website documentation build GHA for 10.1.0 and later

[tkobayas]

Removed the dependency to drools-build-parent because a contributor cannot access drools-build-parent:999-SNAPSHOT easily.

[tkobayas]

FYI)
Steps to move drools-docs into incubator-kie-docs preserving the commit history:
Prerequisite: Install git-filter-repo

# 1. Clone a fresh copy of the drools repo
git clone https://github.com/apache/incubator-kie-drools.git drools-docs-only
cd drools-docs-only

# 2. Filter out everything except the drools-docs/ directory
git filter-repo --path drools-docs/

# 3. Add my incubator-kie-docs repo as a remote and fetch its main branch
git remote add docs [email protected]:tkobayas/kie-docs.git
git fetch docs

# 4. Create import-drools-docs branch off docs/main and merge in the filtered history
git checkout -b import-drools-docs docs/main
git merge --allow-unrelated-histories main

# 5. Resolve any conflicts, commit, then push import-drools-docs to my repo for a PR
git push -u docs import-drools-docs:import-drools-docs

Note: When raising a PR, to preserve the commit history, you have to use "Rebase and merge" rather than "Squash and merge". If the PR contains more than 100 commits, it will hit github rebase limitation (https://docs.github.com/en/repositories/creating-and-managing-repositories/repository-limits#rebase-limits). In that case, you would need to split the PR or directly push without a PR.

When you will do the same for other docs repo, add <module> to the top level pom.xml.

[tkobayas]

This PR cannot Rebase and merge because This branch cannot be rebased due to conflicts. Investigating...

[tkobayas]

This PR cannot be merged because "Rebase and merge" option is limited to 100 commits.

Splitting to 10 PRs:

• Import drools docs (1/10) #4550
• ...