Prompt activation after uv venv has successfully run

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Summary

• Add prompts for users to activate the .venv after it has been created.
• Closes https://github.com/astral-sh/uv/issues/1326

If the platform os matches Os::Windows then we provide the following prompt:

writeln!(
   printer,
   "Activate with .\\{}\\Scripts\\activate.ps1",
   path.normalized_display().cyan()
)

Otherwise we provide the following prompt:

writeln!(
  printer,
  "Activate with source {}/bin/activate",
  path.normalized_display().cyan()
)

I've added additional filters in crates/uv/tests/venv.rs so there shouldn't be issues on any of the CI runs (not sure what some of the Windows paths could look like, so these filters might need to be changed):

        (
            r".*?\\\.venv\\Scripts\\activate\.ps1", 
            "Activate with source /home/ferris/project/.venv/bin/activate"
        )

Test Plan

• Ran tests in crates/uv/tests/venv.rs and updated snapshots.
• Ran uv venv in a Docker container to test that the output is correct (running Ubuntu)