Rollup merge of #146090 - Kobzol:invisible-origin-eq, r=petrochenkov

Derive `PartialEq` for `InvisibleOrigin`

For rust-lang/rust#145354, we need `PartialEq` for `TokenStream` to "just work". However, due to the special comparison implementation that was used for `InvisibleOrigin`, this wasn't the case.

So I derived `PartialEq` for `InvisibleOrigin`, and used the previous special comparison logic only on the single place where it was actually required.

r? `````````@petrochenkov`````````

Author: Zalathar