Fix performance regression when viewing images and tensors

[emilk]

What

• Closes Huge performance regression when hovering large images #3762

When hovering images the InstanceKey corresponds to the hovered pixel value (tensors are mono-components; their elements are their instances). We accidentally were using this instance key as the key for several of our caches, which means we would get constant cache misses when hovering an image, leading to huge performance degradation.

This PR switches to using RowId as the primary key for tensors. In particular, it is the row id of the TensorData component, so I call it tensor_data_row_id everywhere for consistency and clarity. There can never be more than on TensorData per row, and each row has a unique RowId, so this works well.

This simplifies a lot of the code too, removing most uses of VersionedInstancePath and VersionedInstancePathHash.

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[jleibs]

I'm approving for the purposes of fixing the performance issue, but the real bug here in my opinion is:

When hovering images the InstanceKey corresponds to the hovered pixel value (tensors are mono-components; their elements are their instances).

This really feels like an abuse of the definition of instance key which created a foot-gun. InstanceKeys have a very specific meaning with regards to how they should be able to be used in conjunction with queries and changing that meaning on a per-component basis is just asking for trouble in some other generic join / query / filter code in the future.

[emilk]

Yes, it is confusing, but this is in the context of the GPU picking code which uses a hash of the entity path plus an instance key to identify stuff. By reusing the instance key for identifying the pixel in an image, we can read out what pixel the user is hovering exactly, which is pretty useful, but lead to this footgun.