Fix GH-8267: MySQLi uses unsupported format specifier on Windows

Instead of using the unsupported `%I64u` and `%I64d` format specifiers
on Windows, we use the portable `PRIu64` and `PRId

Fix GH-8267: MySQLi uses unsupported format specifier on Windows

Instead of using the unsupported `%I64u` and `%I64d` format specifiers
on Windows, we use the portable `PRIu64` and `PRId64` specifiers.

The `L64()` macro and the `my_longlong` typedef should be adapted as
well, as the `i64` literal suffix is still supported by MSVC, but using
`LL` or `ll` is recommended[1], and the standard `int64_t` is available
there anyway. This is not urgent, though.

[1] <https://docs.microsoft.com/en-us/cpp/cpp/numeric-boolean-and-pointer-literals-cpp?view=msvc-170#integer-literals>

Closes GH-8268.

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