GH-48317: [C++] Use FetchContent for bundled google-cloud-cpp (#48333)

### Rationale for this change

As a follow up of requiring a minimum CMake version >= 3.25 we discussed moving our dependencies from ExternalProject to FetchContent. This can simplify our third party dependency management.

### What changes are included in this PR?

The general change is moving google-cloud-cpp from `ExternalProject` to `FetchContent` and some cleanup to required dependencies that don't require double-installation anymore like Absl and CRC32C

### Are these changes tested?

Yes, the changes are tested locally and on CI.

### Are there any user-facing changes?

No

* GitHub Issue: #48317

Lead-authored-by: Raúl Cumplido <[email protected]>
Co-authored-by: Sutou Kouhei <[email protected]>
Signed-off-by: Sutou Kouhei <[email protected]>

Author: raulcd