feat!: major performance & accuracy improvements in speech-to-text module

[IgorSwat]

Description

This PR introduces several changes to the speech-to-text module based on Whisper models:

• CoreML integration - models re-exported to CoreML backend, bringing significant performance upgrade for iOS devices.
• New streaming algorithm - eliminates duplicates in streaming output, resulting in a major quality improvement of the live streaming mode.
• Changes in demo apps: removed faulty 'voice mode' screen in LLM demo app, refactored speech to text screen in 'speech' app by adding new CoreML models to selection bar and changing the default model for iOS devices.
• Minor code improvements in speech-to-text module

Introduces a breaking change?

• Yes
• No

Change: removes predefined constants for quantized models.
Justification: the quantized models differ very slightly from the original ones, introducing unnecessary complexity in this case.

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 demo app to test the live streaming mode.

Screenshots

Related issues

#1124

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
• My changes generate no new warnings

Additional notes

[msluszniak]

Also if this PR adds breaking change, please describe it directly below Introduces a breaking change? section in PR body.

[msluszniak]

Side note, after merging PR with TTS and rebasing, please make sure that native tests works here after all changes.