LibJS: Follow the spec more closely for tagged template literals

This resolves a FIXME in its code generation, particularly for:
- Caching the template object
- Setting the correct property attributes
- Freezing the resulting objects

This allows archive.org to load, which uses the Lit library.

The Lit library caches these template objects to determine if a
template has changed, allowing it to determine to do a full template
rerender or only partially update the rendering. Before, we would
always cause a full rerender on update because we didn't return the
same template object.

This caused issues with archive.org's code, I believe particularly with
its router library, where we would constantly detach and reattach nodes
unexpectedly, ending up with the page content not being attached to the
router's custom element.

Libraries/LibJS/Bytecode/Generator.h

@@ -348,6 +348,7 @@ public:
 
     [[nodiscard]] size_t next_global_variable_cache() { return m_next_global_variable_cache++; }
     [[nodiscard]] size_t next_property_lookup_cache() { return m_next_property_lookup_cache++; }
+    [[nodiscard]] size_t next_template_object_cache() { return m_next_template_object_cache++; }
 
     enum class DeduplicateConstant {
         Yes,
@@ -426,6 +427,7 @@ private:
     u32 m_next_block { 1 };
     u32 m_next_property_lookup_cache { 0 };
     u32 m_next_global_variable_cache { 0 };
+    u32 m_next_template_object_cache { 0 };
     FunctionKind m_enclosing_function_kind { FunctionKind::Normal };
     Vector<LabelableScope> m_continuable_scopes;
     Vector<LabelableScope> m_breakable_scopes;