`{{XsltSidebar}}` omits some guides under `/web/xslt/`

[bsmth]

The addition of an XSLT Sidebar was intended to reproduce the minimal top-nav on these pages:

previous nav:

These nav elements look hand-picked and omit guides for space-saving reasons.

The new sidebar should include all pages under XPATH and XSLT, considering EXSLT and XML also.

### Tasks
- [ ] Add XSLT guides to XsltSidebar macro
- [ ] Remove usage of {{XSLTRef}} macro in content in favor of {{XsltSidebar}}