[C++] Add an auto fallback solution when system Gtest is compiled with a C++ standard lower than 17.

[HaochengLIU]

Describe the enhancement requested

in PR #34765, Arrow will error out when the detected GTest is compiled with a C++ standard lower than 17. This is a follow-up issue that should support auto fallback:

Proposed solution from @kou :

Add a FindGtestAlt.cmake file (GTestConfig.cmake is a good starting point) and use new target names to refer to suitable Arrow target. See details in this comment

Component(s)

C++

[HaochengLIU]

FYI I need to tackle #34565 first in April as it's related to my job. Once it's done I will revisit this enhancement.

[westonpace]

Do you mean it would fallback to building from source?

[HaochengLIU]

yes, the goal is to support automatic fallback