Make the initializer_list overload of Subarray::set_subarray zero-copy.

[teo-tsirpanis]

Instead of copying it first to a temporary vector, we use std::data to directly pass the initializer_list's data to the C API.

This is the only use of initializer_list in the C++ API, excluding the deprecated Query::set_subarray which was not modified.

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TYPE: CPP_API
DESC: Make the initializer_list overload of Subarray::set_subarray zero-copy.

[eric-hughes-tiledb]

Can I do the same with the overload that takes an std::vector<std::array<T,2>>? Is it guaranteed that the elements are laid out right next to each other in memory?

Don't need a guarantee when unit tests can verify it.

As a rule it's a mistake in C++ to assume any particular memory layout. Alignment, padding, and compiler behavior all come into play.

[teo-tsirpanis]

Or even better a static_assert. This would block at compile-time types with weird layout from being used (like a struct {uint8_t x; uint16_t y;} which will very likely need a padding byte).

[teo-tsirpanis]

Can we merge it as it is? The other overload can be done in a future PR.