Replace all debug_backtrace boilerplate with get_backtrace_loc

[bpfoley]

...which does thing in a way that PHPStan level 7 approves of and can handle missing line numbers or filename in the backtrace info.

NB this produces different DPDatabase log output
"in foo.php on line N" instead of "foo.php:N"

[cpeel]

It feels weird to have this function return leading whitespace -- that was unexpected. I'd rather the callers manage adding whitespace where needed.

[cpeel]

Perhaps something like this:

Suggested change

	$trace = debug_backtrace();
	if (($file = $trace[$depth]["file"] ?? "")) {
	$file = " in $file";
	}
	if (($line = $trace[$depth]["line"] ?? "")) {
	$line = " on line $line";
	}
	return $file . $line;
	$return = [];
	$trace = debug_backtrace();
	if (($file = $trace[$depth]["file"] ?? "")) {
	$return[] = "in $file";
	}
	if (($line = $trace[$depth]["line"] ?? "")) {
	$return[] = "on line $line";
	}
	return join(" ", $return);

[bpfoley]

The leading whitespace is deliberate though: it's there to make it easier on the caller to just append the location to the error message without having to worry about having to insert an extra space when the location isn't empty, eg Undefined property via __set(): ' . $name . get_backtrace_loc()

[cpeel]

Yeah, but we can just:

'Undefined property via __get(): $name ' . get_backtrace_loc(),

[cpeel]

I don't really care if there's a trailing whitespace on exception messages 🤷

[bpfoley]

ACK. Changed as you suggested.