[Dashboards] Fix formatting and accuracy of controls documentation page

[florent-leborgne]

Description

The dashboard controls documentation page (add-controls.md) has formatting and accuracy issues introduced by #5154 (controls as panels for 9.4). This issue tracks the cleanup work in #5664.

Problems:

• Inline {applies_to} directives on standalone lines render as disconnected badges instead of scoping to the content below
• Serverless is missing from most 9.4 version tabs
• Non-standard 9.0-9.3+ applies syntax used throughout
• The 9.4 Options list tab is missing search techniques (Prefix/Contains/Exact) that still exist in the code
• Step numbering is broken (jumps from 6 to 8)
• UI labels don't match the codebase ("Pin to top" vs "Pin to Dashboard", "Save and close" vs "Save")
• The "Edit controls" section doesn't account for the 9.4 panel menu UX (no longer hover-to-reveal)
• No documentation for the "Clear control" action

Fix: PR #5664

Blocked by / Blocks

This issue must be completed before #4951 (search default change from prefix to contains), since #4951 needs the search techniques to be correctly documented in the 9.4 tab first.

Which documentation set does this change impact?

Elastic On-Prem and Cloud (all)

What release is this request related to?

9.4 + Serverless

[florent-leborgne]

More change happened in between and I've been chatting with product about what to do with these pages. The goal is now to present controls as panels, so that will involve moving them and slightly changing the narrative, which I'll do as part of this PR over the next sprint