10400: fix: fix format string highlighting for `todo!` and `unimplemented!` r=jonas-schievink a=jonas-schievink
Part of https://github.com/rust-analyzer/rust-analyzer/issues/10394
These macros require us to see through the `const_format_args!` invocation the panic macros generate, for that we have to add it to our supported built-in macros.
I've also made the macros in the test `#[macro_export]` (turns out they didn't all resolve correctly before this), which changes the output slightly.
bors r+
Co-authored-by: Jonas Schievink <jonasschievink@gmail.com>
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