Grid Generator: support lists of embeds/TIs similar to how lists of Loras are supported

[brendanhoar]

Feature Idea

Testing the impact of Embeddings/TIs is currently somewhat tedious as there is no "automated" support within the Grid generator at the moment.

I propose using the same approach used to integrate Loras into the grid to support adding a dimension of embeddings/TIs, as well as a list of associated weights.

Other

Unlike Loras, location of the embedding/TI within the prompt can be important. The simple approach would be to simply add it to the beginning of the prompt, e.g.

(embed:path/to/embed.safetensors{:embed_weight_if_supplied}),

An alternate or stretch suggestion would be to add a new keyword such as <grid_embed_placeholder> that would indicate to the grid generator where to insert the above embed text in the prompt.