Problem: Confirmation buffer is named with `nvim-pack://` as scheme
prefix and uses buffer id (needed for in-process LSP) as one an entry
in the "hierarchical part".
Solution: Use `nvim://pack-confirm#<buf>` format with a more ubiquitous
`nvim://` prefix and buffer id at the end as the optional fragment.
Problem: In some areas plugin's revision is named "state". This might be
confusing for the users.
Solution: Consistently use "revision" to indicate "plugin's state on
disk".
Problem: No way to granularly operate on plugins when inside
confirmation buffer.
Solution: Implement code actions for in-process LSP that act on "plugin
at cursor":
- Update (if has updates).
- Skip updating (if has updates).
- Delete.
Activate via default `gra` or `vim.lsp.buf.code_action()`.
