GH-45807: [C++] compatibility patches for protobuf 30

[christian-heusel]

Rationale for this change

The current version of arrow is not compatible with protobuf 30.0 and beyond, which we are currently rolling out in Arch Linux:
https://archlinux.org/todo/protobuf-300/

What changes are included in this PR?

In order to migrate to the new APIs based on std::string_view we just use a few casts to std::string.

Are these changes tested?

Compile tested only, but there are no problems expected.

• GitHub Issue: [C++] Arrow is not compatible with protobuf 30 #45807

[github-actions]

Thanks for opening a pull request!

If this is not a minor PR. Could you open an issue for this pull request on GitHub? https://github.com/apache/arrow/issues/new/choose

Opening GitHub issues ahead of time contributes to the Openness of the Apache Arrow project.

Then could you also rename the pull request title in the following format?

GH-${GITHUB_ISSUE_ID}: [${COMPONENT}] ${SUMMARY}

or

MINOR: [${COMPONENT}] ${SUMMARY}

See also:

• Other pull requests
• Contribution Guidelines - Contributing Overview

[assignUser]

Thanks for the contribution, this is not a minor PR though. I will create and link an issue for you!

[github-actions]

⚠️ GitHub issue #45807 has been automatically assigned in GitHub to PR creator.

[assignUser]

Could you apply this diff to fix the format: https://github.com/apache/arrow/actions/runs/13872657236/job/38822487820?pr=45805#step:6:33

[christian-heusel]

Thanks for creating the issue, I have added the reference to it in the latest version of the commit an applied the formatting changes 🤗

Edit: Argh, created a whitespace issue with my editor, now applied it with clang-format manually 😅

[kou]

@github-actions crossbow submit -g cpp

[github-actions]

Revision: 6994dac

Submitted crossbow builds: ursacomputing/crossbow @ actions-4471dd3b4d

Task	Status
example-cpp-minimal-build-static
example-cpp-minimal-build-static-system-dependency
example-cpp-tutorial
test-alpine-linux-cpp
test-build-cpp-fuzz
test-conda-cpp
test-conda-cpp-meson
test-conda-cpp-valgrind
test-cuda-cpp-ubuntu-22.04-cuda-11.7.1
test-debian-12-cpp-amd64
test-debian-12-cpp-i386
test-fedora-39-cpp
test-ubuntu-22.04-cpp
test-ubuntu-22.04-cpp-20
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