[Issue 18388] std.experimental.logger slow performance

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18388

--- Comment #12 from Robert Schadek <rburners at gmail.com> ---
Building the string in memory will put quite some pressure on the GC.
Using a stack based array is limiting and not @safe.

formattedWrite can do more than printf.

I stayed away from allowing configurations, because it is really hard to know
what should be a config option and what not.
So the idea is to inherit and change in code what need to be different.

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