Miri: implement arbitrary-self dyn receivers Roughly follows the [codegen logic](851fcc7a54/compiler/rustc_codegen_ssa/src/mir/block.rs (L809)). Fixes https://github.com/rust-lang/miri/issues/1038 r? `@oli-obk` Cc `@eddyb`
851fcc7a54/compiler/rustc_codegen_ssa/src/mir/block.rs (L809)