feat: add gemini-2.0-flash-exp and gemini-exp-1206 models

[raphaelchristi]

Description

This PR adds support for two new Google Gemini models:

• gemini-2.0-flash-exp
• gemini-exp-1206

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #5213 will degrade performances by 73.5%

_{Comparing raphaelchristi:feat/add-new-gemini-models (cd424ac) with main (222f15d)}

Summary

⚡ 2 improvements
❌ 2 regressions
✅ 11 untouched benchmarks

:warning: Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	raphaelchristi:feat/add-new-gemini-models	Change
⚡	test_get_and_cache_all_types_dict	1,088.1 µs	948.6 µs	+14.71%
❌	test_load_flows	1.1 ms	4 ms	-73.5%
❌	test_setup_llm_caching	1.2 ms	4 ms	-70.33%
⚡	test_successful_run_with_input_type_any	255.4 ms	214.4 ms	+19.12%

[edwinjosechittilappilly]

@raphaelchristi did you test it?

[raphaelchristi]

@edwinjosechittilappilly yes , i tested It.