Allow saving prompts from the Prompt Manager (#12359)

Adds the following features to the prompt manager:

- New prompt – Create a new prompt from the UI. It will only persist if
it is saved.
- Save prompt – Save a prompt by clicking the save button in the UI. A
keybinding will be added for this in the future.
- Reveal prompt - Show the selected prompt on the file system. Only
available for saved prompts.

New prompts that are saved will use the
`{slugified_title}_{ver}_{id}.md` format which all imported prompts will
move to in the near future.

Also orders prompts in alphabetical order by default.

Release Notes:

- N/A

crates/ui/src/components/icon.rs

@@ -164,6 +164,8 @@ pub enum IconName {
     ReplaceNext,
     ReplyArrowRight,
     Return,
+    Reveal,
+    Save,
     Screen,
     SelectAll,
     Server,
@@ -277,10 +279,12 @@ impl IconName {
             IconName::Quote => "icons/quote.svg",
             IconName::Regex => "icons/regex.svg",
             IconName::Replace => "icons/replace.svg",
+            IconName::Reveal => "icons/reveal.svg",
             IconName::ReplaceAll => "icons/replace_all.svg",
             IconName::ReplaceNext => "icons/replace_next.svg",
             IconName::ReplyArrowRight => "icons/reply_arrow_right.svg",
             IconName::Return => "icons/return.svg",
+            IconName::Save => "icons/save.svg",
             IconName::Screen => "icons/desktop.svg",
             IconName::SelectAll => "icons/select_all.svg",
             IconName::Server => "icons/server.svg",