The SDF_FORMAT_ARGS `usdMjcfToggleUsdPhysics` is introduced to toggle writing UsdPhysics or not when converting. Off by default
PiperOrigin-RevId: 746467942
Change-Id: I26cb9a4c4ae2eef96163dab967a74f14940a2a6d
We will still need to tag these with a custom API schema to ease round-tripping but that will follow creation of such a schema.
PiperOrigin-RevId: 746421793
Change-Id: I2df2209b4bc90d763718fb4bea8158b8598755c6