Support multiple targets in rust-analyzer with cargo 1.64.0+

[poliorcetics]

The 1.64.0 release notes mention that cargo now accepts several targets at once to build for all of them.

Is it possible to integrate this in rust-analyzer so we can get warnings for several targets without changing the config ?

If someone knows where to start, I can try to do it, provided it doesn't needs days and days of coding

[Veykril]

#13290 implemented this