fix(treesitter): make tests for memoize more robust

Instead of painfully messing with timing to determine if queries were
reparsed, we can simply keep a counter next to the call to ts_query_new

Also memoization had a hidden dependency on the garbage collection of
the the key, a hash value which never is kept around in memory. this was
done intentionally as the hash does not capture all relevant state for the
query (external included files) even if actual query objects still
would be reachable in memory. To make the test fully deterministic in
CI, we explicitly control GC.

src/nvim/lua/treesitter.c

@@ -1318,6 +1318,7 @@ int tslua_parse_query(lua_State *L)
   size_t len;
   const char *src = lua_tolstring(L, 2, &len);
 
+  tslua_query_parse_count++;
   uint32_t error_offset;
   TSQueryError error_type;
   TSQuery *query = ts_query_new(lang, src, (uint32_t)len, &error_offset, &error_type);

src/nvim/lua/treesitter.h

@@ -1,7 +1,12 @@
 #pragma once
 
 #include <lua.h>  // IWYU pragma: keep
+#include <stdint.h>
+
+#include "nvim/macros_defs.h"
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "lua/treesitter.h.generated.h"
 #endif
+
+EXTERN uint64_t tslua_query_parse_count INIT( = 0);