Remove deprecated rust macros

Summary: With D81048274, there should no longer be any usages of `fbcode_macros//build_defs:rust_(library|binary|unittest).bzl`. Nor `fbsource//tools/build_defs:rust.bzl`

Reviewed By: dtolnay

Differential Revision: D81059818

fbshipit-source-id: 13cada1d4ee4d67725d0e89328068bd64e9d9690

Author: capickett