DynamicConfig: use canonical clone impl

[hkBst]

Fixes clippy warning:

warning: non-canonical implementation of `clone` on a `Copy` type
  --> compiler/rustc_query_impl/src/lib.rs:60:29
   |
60 |       fn clone(&self) -> Self {
   |  _____________________________^
61 | |         DynamicConfig { dynamic: self.dynamic }
62 | |     }
   | |_____^ help: change this to: `{ *self }`

[rustbot]

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[hkBst]

I tried changing the manual Copy and Clone impls to a derive clause, but that ends up causing lots of unsatisfied trait bounds. I don't understand why that does not work. The single shared reference member should impl Copy, and the automatically derived impls should be identical to the manual impls AFAICT. Apparently I'm wrong about this somehow. Would love to understand!