GH-50728: [C++] Remove call_traits::argument_count in favor of type_traits

[taepper]

Rationale for this change

As part of #50250 we slowly want to remove the custom metaprogramming helpers

What changes are included in this PR?

This removes call_traits::argument_count in favor of type_traits.

We could also remove ContinueFuture::ForSignature because std::invoke_result already checks the signature.

Are these changes tested?

Yes.

Are there any user-facing changes?

No

• GitHub Issue: [C++] Remove call_traits::argument_count #50728

[github-actions]

⚠️ GitHub issue #50728 has been automatically assigned in GitHub to PR creator.

[taepper]

bump @HuaHuaY @kou @pitrou

[pitrou]

@github-actions crossbow submit -g cpp

[github-actions]

Revision: 6c95106

Submitted crossbow builds: ursacomputing/crossbow @ actions-1da1365e24

Task	Status
example-cpp-minimal-build-static
example-cpp-minimal-build-static-system-dependency
example-cpp-tutorial
test-build-cpp-fuzz
test-conda-cpp
test-conda-cpp-valgrind
test-debian-13-cpp-amd64
test-debian-13-cpp-i386
test-debian-experimental-cpp-gcc-15
test-fedora-42-cpp
test-ubuntu-22.04-cpp
test-ubuntu-22.04-cpp-bundled
test-ubuntu-22.04-cpp-emscripten
test-ubuntu-22.04-cpp-no-threading
test-ubuntu-24.04-cpp
test-ubuntu-24.04-cpp-bundled-offline
test-ubuntu-24.04-cpp-gcc-13-bundled
test-ubuntu-24.04-cpp-gcc-14
test-ubuntu-24.04-cpp-minimal-with-formats
test-ubuntu-24.04-cpp-thread-sanitizer

[pitrou]

Thanks a lot @taepper . The CI failures are unrelated, I'll merge.