Support output dimensionality for embedding models

[marcelogdeandrade]

Checked

• I searched existing ideas and did not find a similar one
• I added a very descriptive title
• I've clearly described the feature request and motivation for it

Feature request

Recent Gemini Embedding models support elastic output dimensionality as explained here.

Google's library enables a config called output_dimensionality which fixes the desired dimensionality of the model used. This request is basically to do the same thing on GoogleGenerativeAIEmbeddings

Motivation

It is essential to fix output dimensionality for RAG systems, and given recent elastic output dimensionality for state of the art embedding models, such as gemini-embedding-exp-03-07, this feature will have a big impact.

Proposal (If applicable)

Add new configuration to GoogleGenerativeAIEmbeddings and enable output_dimensionality as its config.