Add threadpool threadcap for AArch64 builds
@penpornk  Hi @penpornk, Can you please review this PR ? Thank you! Hi @penpornk, would you mind taking a look at this PR and let me know if any changes are needed? Thank you :)  > Thank you for the PR and sorry for the delay! Could you please paste some microbenchmarks/end-to-end model performance results before and after the changes?
> 
> cc: @cantonios

Please find attached benchmarks on image classification models before and after this PR. It improves performance up to 8% with an average of a 4.5% improvement.

![benchmarks_cv_threadcap](https://github.com/tensorflow/tensorflow/assets/117736650/b6a31a10-05b4-4702-b4d9-5beac033e549)
 Hi @penpornk are there any other changes required on my end to get this PR merged? Thanks. Hi @penpornk and @cantonios. Would it be possible to get this merged in soon so that it makes it for the next release? Thank you. @davsva01 Sorry for the delay! Our auto-import tool failed with TSL-only changes. I'll try to manually import the changes.
Runs thread pool with one thread less when number of cores == num_threads and num_threads >= 16. This fixes a performance degradation issue on AArch64 builds when using max threads on systems with a large amount of cores.