* docs/multiplexing: overhaul plugin documentation
* update nav data
* remove dupe nav data
* add external plugin section to index
* move custom plugin backends under internals/plugins
* remove ref to moved page
* revert moving custom plugin backends
* add building plugins from source section to plug dev
* add mux section to plugin arch
* add mux section to custom plugin page
* reorder custom database page
* use 'external plugin' where appropriate
* add link to plugin multiplexing
* fix example serve multiplex func call
* address review comments
* address review comments
* Minor format updates (#14590)
* mv Plugins to top-level; update upgrading plugins
* update links after changing paths
* add section on external plugin scaling characteristics
* add updates on plugin registration in plugin management page
* add plugin learn resource
* be more explicit about mux upgrade steps; add notes on when to avoid db muxing
* add plugin upgrade built-in section
* add caveats to built-in plugin upgrade
* improvements to built-in plugin override
* formatting, add redirects, correct multiplexing use case
* fix go-plugin link
* Apply suggestions from code review
Co-authored-by: Loann Le <84412881+taoism4504@users.noreply.github.com>
* remove single item list; add link to Database interface
Co-authored-by: Yoko Hyakuna <yoko@hashicorp.com>
Co-authored-by: Loann Le <84412881+taoism4504@users.noreply.github.com>
