chore: Add model selections and small fixes

[msluszniak]

Description

Introduces a breaking change?

• Yes
• No

Type of change

• Bug fix (change which fixes an issue)
• New feature (change which adds functionality)
• Documentation update (improves or adds clarity to existing documentation)
• Other (chores, tests, code style improvements etc.)

Tested on

• iOS
• Android

Testing instructions

Run models from demo apps and check if you can select different models and they works:

• Computer Vision
• LLM
• Speech

Additionally:

• Check that without registering streamInsert demo app with text to speech fails
• Check that without changes in OCR and Vertical OCR demo app fails
• Check that text to image example looks now simpler and better
• Check that image embeddings example works

Screenshots

Related issues

Closes #958

Checklist

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation accordingly (Not applicable)
• My changes generate no new warnings

Additional notes

Additionally, I found out that links for VLMs are incorrect since they point out to main on hugging face. @NorbertKlockiewicz could you create 0.8.0 tag on huggingface as for lfm instruct and change links here: https://github.com/software-mansion/react-native-executorch/blob/main/packages/react-native-executorch/src/constants/modelUrls.ts#L408-L411?
Thanks

[msluszniak]

@barhanc @IgorSwat I addressed your suggestions, also fixed image embeddings demo app, please check this during re-review.