Auto Save All Buffers After A Delay (helix-editor#10899)

* auto save after delay

* configable

* clearer names

* init

* working with some odd behaviour

* working with greater consistency

* Apply reviewer suggestions

- Remove unneccessary field
- Remove blocking save

* Improve auto-save configuration

Auto save can be configured to trigger on focus loss:
```toml
auto-save.focus-lost = true|false
```

and after a time delay (in milli seconds) since last keypress:
```toml
auto-save.after-delay.enable = true|false
auto-save.after-delay.timeout = [0, u64::MAX] # default: 3000
```

* Remove boilerplate and unnecessary types

* Remove more useless types

* Update docs for auto-save.after-delay

* Fix wording of (doc) comments relating to auto-save

* book: Move auto-save descriptions to separate section

---------

Co-authored-by: Miguel Perez <[email protected]>
Co-authored-by: Miguel Perez <[email protected]>

helix-term/src/handlers.rs

@@ -32,6 +32,6 @@ pub fn setup(config: Arc<ArcSwap<Config>>) -> Handlers {
 
     completion::register_hooks(&handlers);
     signature_help::register_hooks(&handlers);
-    diagnostics::register_hooks(&handlers);
+    auto_save::register_hooks(&handlers);
     handlers
 }