Add output attribute to camera elements.

This attribute allows specifying the intended output types (e.g., RGB, depth, normal) for each camera in the XML. The output types are stored as bit flags in `mjModel`.

PiperOrigin-RevId: 853316261
Change-Id: I2aa4c30867938af88af36ca49cee559e9d0d4590

Author: yuvaltassa

dm_control/mjcf/schema.xml

@@ -350,6 +350,7 @@
             <attribute name="zaxis" type="array" array_type="float" array_size="3"/>
             <attribute name="euler" type="array" array_type="float" array_size="3"/>
             <attribute name="resolution" type="array" array_type="int" array_size="2"/>
+            <attribute name="output" type="string"/>
             <attribute name="focal" type="array" array_type="float" array_size="2"/>
             <attribute name="focalpixel" type="array" array_type="float" array_size="2"/>
             <attribute name="principal" type="array" array_type="float" array_size="2"/>
@@ -675,6 +676,7 @@
                 <attribute name="zaxis" type="array" array_type="float" array_size="3"/>
                 <attribute name="euler" type="array" array_type="float" array_size="3"/>
                 <attribute name="resolution" type="array" array_type="int" array_size="2"/>
+                <attribute name="output" type="string"/>
                 <attribute name="focal" type="array" array_type="float" array_size="2"/>
                 <attribute name="focalpixel" type="array" array_type="float" array_size="2"/>
                 <attribute name="principal" type="array" array_type="float" array_size="2"/>
@@ -1125,6 +1127,7 @@
             <attribute name="zaxis" type="array" array_type="float" array_size="3"/>
             <attribute name="euler" type="array" array_type="float" array_size="3"/>
             <attribute name="resolution" type="array" array_type="int" array_size="2"/>
+            <attribute name="output" type="string"/>
             <attribute name="focal" type="array" array_type="float" array_size="2"/>
             <attribute name="focalpixel" type="array" array_type="float" array_size="2"/>
             <attribute name="principal" type="array" array_type="float" array_size="2"/>
@@ -1502,6 +1505,7 @@
                 <attribute name="zaxis" type="array" array_type="float" array_size="3"/>
                 <attribute name="euler" type="array" array_type="float" array_size="3"/>
                 <attribute name="resolution" type="array" array_type="int" array_size="2"/>
+                <attribute name="output" type="string"/>
                 <attribute name="focal" type="array" array_type="float" array_size="2"/>
                 <attribute name="focalpixel" type="array" array_type="float" array_size="2"/>
                 <attribute name="principal" type="array" array_type="float" array_size="2"/>