Make script parameter optional in py_console_script_binary

[hofbi]

Match what rules_python is doing in https://github.com/bazel-contrib/rules_python/blob/d0b9baadc43eff92b3b9df0a04343e7ca653c44a/python/private/py_console_script_binary.bzl#L68-L69

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Changes are visible to end-users: yes

• Searched for relevant documentation and updated as needed: yes/no
• Breaking change (forces users to change their own code or config): yes/no
• Suggested release notes appear below: yes/no

Test plan

• Covered by existing test cases
• New test cases added
• Manual testing; please provide instructions so we can reproduce:

[aspect-workflows]

Bazel 8 (Test)

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Bazel 8 (Test)

e2e

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Bazel 9 (Test)

e2e

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Bazel 8 (Test)

examples/uv_pip_compile

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1 test (100.0%) was fully cached saving 444ms.