clone wasm store engine (#3542)

This resolves https://github.com/tree-sitter/tree-sitter/issues/3454.

This brings the usage of wasmtime::Engine in line with how wasmtime
intends it to be used. All wasmtime functions that receive an Engine
always receive an `&Engine`, never an owned `Engine`.  They are always
responsible for cloning the reference if they need it.

This brings the usage of wasmtime::Engine in line with how TSParser
treats TSLanguages: when setting a language to the parser, the parser is
responsible for cloning the reference to the TSLanguage. It is
counterintuitive for TSParser to have different behavior when receiving
wasmtime_engine_t.

C API users also expect this behavior, see "Memory Management"
[here](https://docs.wasmtime.dev/c-api/wasm_8h.html). Talking about the
C API: without this change, failing to clone the `wasmtime_engine_t`
(which, again, is never something API users need to do in wasmtime) and
then reusing the engine in multiple TSLanguages results in a use after
free. With this change, failing to call `wasm_engine_delete` on your
owned Engine results in a memory leak. Memory leaks are safer than
use-after-free.

cli/loader/src/lib.rs

@@ -1198,7 +1198,7 @@ impl Loader {
     }
 
     #[cfg(feature = "wasm")]
-    pub fn use_wasm(&mut self, engine: tree_sitter::wasmtime::Engine) {
+    pub fn use_wasm(&mut self, engine: &tree_sitter::wasmtime::Engine) {
         *self.wasm_store.lock().unwrap() = Some(tree_sitter::WasmStore::new(engine).unwrap());
     }