Review and remove old duplicate tools reference pages

As part of the work in DOC-5647, it was identified that some tools reference pages were still being built from old source in the docs-server repo, even though these pages had moved over to being built from the same source as the command line help files. This was corrected by deleting the duplicate/outdated versions from the docs-server repo, updating the nav with the new paths, and adding page aliases to the new shared source files in the couchbase-cli repo.

However, as a precautionary measure, the old source files were copied to the following directory in the couchbase-cli repo: https://github.com/couchbase/couchbase-cli/tree/master/docs/modules/cli/pages/cbtools/old

As a result, these pages are still being built into the docs site: https://docs.couchbase.com/server/current/cli/cbtools/old/cbbackup-tool.html

They are not referenced in the nav anywhere, but they do appear in site search and probably messing with SEO.

These duplicate pages should be removed from each branch going back to when they were introduced in 6.5.

• Short-term fix: Make Antora ignore these files by adding a period to the beginning of every filename in docs/modules/cli/pages/cbtools/old/
• Long-term fix (if desired): Compare the old pages with the new shared-source ones to see if there's anything that's missing and worth adding back to the shared-source pages. Then delete the old pages.