[chore](compile) fix macos compile be failed

[zy-kkk]

1. Follow PR [env](compilation) open implicit-int-conversion check  #55634: Fix implicit type conversion warnings on macOS

   • Added static_cast<int>() for vm_page_size, memory_pressure/10, and _s_disks.size()
   • These warnings only appear on macOS due to platform-specific type differences (vm_size_t vs int)

2. Follow PR [enhancement](filecache) parallel clear cache between multiple cache instance #55259: Fix std::execution::par compatibility on macOS

   • Added conditional compilation for std::execution::par which is not available in macOS libc++
   • Preserves parallel execution on Linux while maintaining compatibility on macO

[Thearas]

Thank you for your contribution to Apache Doris.
Don't know what should be done next? See How to process your PR.

Please clearly describe your PR:

1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
3. What features were added. Why was this function added?
4. Which code was refactored and why was this part of the code refactored?
5. Which functions were optimized and what is the difference before and after the optimization?

[zy-kkk]

run buildall

[zy-kkk]

fixed by https://github.com/apache/doris/pull/55860，fix this