[SAoC 2022] Replace druntime Hooks with Templates: Milestone 1, Week 4

[Teodor Dutu]

It turned out that the bug I mentioned [last 
week](https://forum.dlang.org/thread/qfgmeklvbdptvzwwpkbe@forum.dlang.org) regarding `__FUNCTION__` was [unrelated to my work](https://issues.dlang.org/show_bug.cgi?id=23408) and is now [being fixed](https://github.com/dlang/dmd/pull/14549). To unblock my PR, I moved the [failing test](https://github.com/dlang/dmd/blob/81f5c8b354aed2dc53a45e52498dc23f2f40fe88/compiler/test/runnable/test19688.d) to `compilable/`, as suggested in [my PR](https://github.com/dlang/dmd/pull/14550).