fix: correctly update tool calls in AIMessages

[andreitava-uip]

Modifying the dedicated tool_call property is not enough. We need to modify the actual content parts.
This is done via Langchain's normalized content blocks, which are supported in all chat model clients we use.

@valentinabojan implemented the guardrails commit (got lost in rebase/force push somewhere)

Development Package

• Add this package as a dependency in your pyproject.toml:

[project]
dependencies = [
  # Exact version:
  "uipath-langchain==0.4.27.dev1004532169",

  # Any version from PR
  "uipath-langchain>=0.4.27.dev1004530000,<0.4.27.dev1004540000"
]

[[tool.uv.index]]
name = "testpypi"
url = "https://test.pypi.org/simple/"
publish-url = "https://test.pypi.org/legacy/"
explicit = true

[tool.uv.sources]
uipath-langchain = { index = "testpypi" }