[deque] fix: constexpr support for deque in C++23

[SekaiArendelle]

Summary

• Add constexpr allocation/deallocation paths (using new[]/delete[]) in deque for C++26 constant evaluation
• Fix deque_destroy_trivial_common_align null-pointer guard and controller deallocation in consteval
• Fix overlapped_copy_trivial to use construct_at on output in consteval context
• Guard __builtin_operator_new/__builtin_operator_delete with FAST_IO_HAS_BUILTIN for portability
• Replace __builtin_is_constant_evaluated with #if __cpp_if_consteval + if consteval pattern
• Add constexpr deque test (push/pop/back/front, copy/move/assign/swap, iterators, growth)

[SekaiArendelle]

Seems the compiler inside ci is quite old. To prove my patch can work properly, following is what I copy-paste from my terminal:

PS D:\projects\fast_io> clang++ .\tests\0026.container\0003.deque\constexpr.cc -o .\build\test.exe -std=c++26 -I .\include\ -lntdll
PS D:\projects\fast_io> clang++ .\tests\0026.container\0003.deque\constexpr.cc -o .\build\test.exe -std=c++23 -I .\include\ 
PS D:\projects\fast_io> g++ .\tests\0026.container\0003.deque\constexpr.cc -o .\build\test.exe -std=c++23 -I .\include\ 
PS D:\projects\fast_io> clang++ .\tests\0026.container\0003.deque\constexpr.cc -o .\build\test.exe -std=c++23 -I .\include\ -fexperimental-new-constant-interpreter
PS D:\projects\fast_io> g++ --version
g++.exe (x86_64-win32-seh-rev0, Built by MinGW-Builds project) 16.1.0
Copyright (C) 2026 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

PS D:\projects\fast_io> clang++ --version
clang version 23.0.0git (https://github.com/llvm/llvm-project.git 4c4c1db7c69a6fda6cfa6bc6066bb09a433edc89)
Target: x86_64-unknown-windows-gnu
Thread model: posix
InstalledDir: D:/toolchains/llvm/x86_64-windows-gnu/bin
PS D:\projects\fast_io>