Add source location information to log messages

[bradallred]

Log messages are queued so you have to search the code for the non variable bits to locate their origin.

We should add something like std::source_location to attach that information. __FILE__ and __LINE__ macros can do this since std::source_location is C++20.

This should probably only be put into debug builds to keep pollution down.

Originally posted by @bradallred in #1900 (comment)

[lynxlynxlynx]

I don't see what's there to gain, the backtrace was clear once the main thread was printed.

[bradallred]

It's just small effort that can help in certain situations. The logging happens on another thread it's not always going to be clear since we currently have 2 threads that can continue executing before the message is even processed. The number of threads is only likely to grow.

[lynxlynxlynx]

All the important work is done by the main thread, so it still seems like a wild hypothetical.