[FIX] base: speedup generate_assets_nodes

is_transpiled is only needed when generating a asset bundle while
JavascriptAsset can be generated to compute the version hash.

is_transpiled needs to read the content to be defined which is quite
slow. Transforming is_transpiled into a lazy property will speedup the
cold loading of generate_assets_node, especially when attachment already
exists.

Locally:
- /web with all modules in debug=assets goes from ~350 to ~150 ms
- generate_assets_nodes part goes from ~230 to ~55 ms

closes odoo/odoo#116035

Signed-off-by: Simon Genin (ges@odoo) <ges@odoo.com>

odoo/addons/base/models/assetsbundle.py

@@ -987,9 +987,15 @@ class JavascriptAsset(WebAsset):
 
     def __init__(self, bundle, inline=None, url=None, filename=None):
         super().__init__(bundle, inline, url, filename)
-        self.is_transpiled = is_odoo_module(super().content)
+        self._is_transpiled = None
         self._converted_content = None
 
+    @property
+    def is_transpiled(self):
+        if self._is_transpiled is None:
+            self._is_transpiled = bool(is_odoo_module(super().content))
+        return self._is_transpiled
+
     @property
     def content(self):
         content = super().content