ATrace C++ wrapper API

Forked from https://github.com/android-ndk/ndk/issues/476

Possible API:

```C++
namespace android::trace {
class Trace final {
public:
Trace (const std::string& sectionName);
Trace (std::string_view sectionName);
~Trace (); // Use RAII to close trace section

static bool isEnabled() noexcept;
static void beginSection(const std::string& sectionName) noexcept;
static void beginSection(std::string_view sectionName) noexcept;
static void endSection() noexcept;
};
}
```

Review the linked android-ndk/ndk#476 discussion and compare its requirements with the proposed android::trace::Trace API. Done means the proposed C++ wrapper is implemented with the listed RAII and static tracing operations, but this issue names no implementation files or tests.

Written by the indexing model from the issue text.