feat: improve the code sample for std::inplace_vector

[YukunJ]

Brief: improve the code sample for std::inplace_vector section.

Since the tutorial is explicitly mentioning

a.

最讨喜的一个性质是：当 T 是 trivially copyable 时，inplace_vector<T, N> 本身也是 trivially copyable
doc: https://cppreference.com/cpp/container/inplace_vector/try_push_back

b.

容量超限时的行为也设计得克制：push_back 超过 N 会抛 std::bad_alloc（异常关闭时退化为 terminate），而想避免异常可以用 C++26 的 try_push_back/try_emplace_back，它们超限时不抛、返回一个错误指示，适合 -fno-exceptions 环境。

It's worthwhile to show these two points in the code sample.

QA:
see godbolt link https://godbolt.org/z/K78EnTnYM

@Charliechen114514