rust: Drop rust-llvm

rust: Drop rust-llvm

Drop rust-llvm recipe because now rust depends on clang for building

*Dropped Patches:

0001-libunwind-Use-gcs-instead-of-gcs-target-attribute.patch(Merged)
https://github.com/llvm/llvm-project/commit/b46f34452e9dec50eee6ddbe07875f05e421a81c

0001-AsmMatcherEmitter-sort-ClassInfo-lists-by-name-as-we.patch
0002-llvm-allow-env-override-of-exe-path.patch
(We have the above two patches in clang)

Signed-off-by: Deepesh Varatharajan <Deepesh.Varatharajan@windriver.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>