Fix LLM parameter propagation and refactor BrowserUseTool

[rjambrecic]

Why are these changes needed?

Related issue number

Closes #985

Checks

• I've included any doc changes needed for https://docs.ag2.ai/. See https://docs.ag2.ai/docs/contributor-guide/documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov]

Codecov Report

Attention: Patch coverage is 90.47619% with 14 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
autogen/import_utils.py	75.00%	3 Missing and 4 partials ⚠️
...ools/experimental/browser_use/langchain_factory.py	95.61%	2 Missing and 3 partials ⚠️
...ogen/tools/experimental/browser_use/browser_use.py	50.00%	1 Missing ⚠️
autogen/tools/experimental/crawl4ai/crawl4ai.py	66.66%	1 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (5d2f165) and HEAD (5dfc518). Click for more details.

HEAD has 67 uploads less than BASE

Flag	BASE (5d2f165)	HEAD (5dfc518)
3.9	75	73
ubuntu-latest	143	119
3.10	95	93
interop	13	9
crawl4ai	13	9
browser-use	7	3
3.11	67	51
retrievechat	15	14
teachable	4	3
lmm	4	3
gemini	15	14
falkordb	2	0
autobuild	1	0
deepseek	1	0
neo4j	2	0
openai	1	0

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