TTS/STT: Proof of Concept implementation for STT eval

[Prajna1999]

1. PoC implementation of STT eval for below providers along with Word Error Rate and Lenient Word Error Rate for the below providers.
   • Gemini-2.5-pro
   • Gemin-2.5-flash
   • Gemini-3
   • Chirp V3 (Google-STT)
   • OpenAI - Whisper -1
   • OpenAI - OpenAI-4o-transcribe
   • AI4Bharat
   • Bhasini

Evaluation metrics
- WER
- Lenient WER
- Average scores
- Count of errors insertion, substitution, deletion.
- Summary scores