Reset Hydra texture state when render product changes

[sylvesterkaczmarek]

Description

Make IsaacAttachHydraTexture correctly follow changes to inputs:renderProductPrim.

The node caches both its Hydra texture and the set of render vars it has already applied. Previously that cache was not associated with a render-product path, so changing the target could leave the existing texture bound to the previous render product while render vars were incorrectly treated as already applied.

Track the current render-product path in the internal state. When the target changes, disable and release the cached texture, clear the applied render-var cache and timeline subscriptions, and let the normal compute path create a fresh attachment for the new target. Re-evaluating the same target keeps the existing cached state.

Validation

• adds a focused test that switches render products and verifies cached texture/render-var state is cleared
• verifies the previous texture is disabled before it is released
• adds a same-target test confirming existing cached state is preserved
• production change is limited to OgnIsaacAttachHydraTexture.py