Replace name attribute with setters and getters in the C API of mjSpec.

PiperOrigin-RevId: 778816015
Change-Id: Ieffb7a5bce37e887ff009f9a02d2434435e79ca1

src/user/user_api.h

@@ -339,6 +339,9 @@ MJAPI mjsPlugin* mjs_asPlugin(mjsElement* element);
 
 //---------------------------------- Attribute setters ---------------------------------------------
 
+// Set element's name.
+MJAPI void mjs_setName(mjsElement* element, const char* name);
+
 // Copy buffer.
 MJAPI void mjs_setBuffer(mjByteVec* dest, const void* array, int size);
 
@@ -375,6 +378,9 @@ MJAPI void mjs_setPluginAttributes(mjsPlugin* plugin, void* attributes);
 
 //---------------------------------- Attribute getters ---------------------------------------------
 
+// Get element's name.
+MJAPI mjString* mjs_getName(mjsElement* element);
+
 // Get string contents.
 MJAPI const char* mjs_getString(const mjString* source);