Allow benchmark test to be build with CRT Client

[sbiscigl]

Description of changes:

Defaults the benchmark tests to use CRT client, can be optionally turned off. ie.

Build benchmarks with CRT client: -DBUILD_ONLY="s3;s3-crt;monitoring" -DBUILD_BENCHMARKS=ON -DAWS_SDK_BENCHMARK_USE_CRT=ON

Build benchmarks with vanilla client: -DBUILD_ONLY="s3;s3-crt;monitoring" -DBUILD_BENCHMARKS=ON -DAWS_SDK_BENCHMARK_USE_CRT=OFF

Check all that applies:

• [x] Did a review by yourself.
• [x] Added proper tests to cover this PR. (If tests are not applicable, explain.)
• [x] Checked if this PR is a breaking (APIs have been changed) change.
• [x] Checked if this PR will not introduce cross-platform inconsistent behavior.
• [x] Checked if this PR would require a ReadMe/Wiki update.

Check which platforms you have built SDK on to verify the correctness of this PR.

• [ ] Linux
• [ ] Windows
• [ ] Android
• [x] MacOS
• [ ] IOS
• [ ] Other Platforms

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.