LSP Optimization: Wrap programs_cache in an Arc (#5472)

## Description
We clone the `Engines` before each keystroke in the language server. We
shouldn't need to clone anything other than a pointer for the
`programs_cache`. Measured against the `benchmark` example in `sway-lsp`
tests, this saves us `23.015ms`.

related to #5445 

## Checklist

- [x] I have linked to any relevant issues.
- [ ] I have commented my code, particularly in hard-to-understand
areas.
- [ ] I have updated the documentation where relevant (API docs, the
reference, and the Sway book).
- [ ] I have added tests that prove my fix is effective or that my
feature works.
- [ ] I have added (or requested a maintainer to add) the necessary
`Breaking*` or `New Feature` labels where relevant.
- [x] I have done my best to ensure that my PR adheres to [the Fuel Labs
Code Review
Standards](https://github.com/FuelLabs/rfcs/blob/master/text/code-standards/external-contributors.md).
- [x] I have requested a review from the relevant team or maintainers.

sway-core/src/query_engine/mod.rs

@@ -47,15 +47,15 @@ pub type ProgramsCacheMap = HashMap<ModulePath, ProgramsCacheEntry>;
 
 #[derive(Debug, Default)]
 pub struct QueryEngine {
-    parse_module_cache: RwLock<ModuleCacheMap>,
-    programs_cache: RwLock<ProgramsCacheMap>,
+    parse_module_cache: Arc<RwLock<ModuleCacheMap>>,
+    programs_cache: Arc<RwLock<ProgramsCacheMap>>,
 }
 
 impl Clone for QueryEngine {
     fn clone(&self) -> Self {
         Self {
-            parse_module_cache: RwLock::new(self.parse_module_cache.read().unwrap().clone()),
-            programs_cache: RwLock::new(self.programs_cache.read().unwrap().clone()),
+            parse_module_cache: self.parse_module_cache.clone(),
+            programs_cache: self.programs_cache.clone(),
         }
     }
 }
@@ -67,11 +67,10 @@ impl QueryEngine {
     }
 
     pub fn insert_parse_module_cache_entry(&self, entry: ModuleCacheEntry) {
-        let mut cache = self.parse_module_cache.write().unwrap();
         let path = entry.path.clone();
         let include_tests = entry.include_tests;
-
         let key = ModuleCacheKey::new(path, include_tests);
+        let mut cache = self.parse_module_cache.write().unwrap();
         cache.insert(key, entry);
     }