Split BPF loader to match the rest of the programs (#4636)

programs/bpf_loader_program/src/lib.rs

@@ -0,0 +1,12 @@
+#[macro_export]
+macro_rules! solana_bpf_loader_program {
+    () => {
+        (
+            "solana_bpf_loader_program".to_string(),
+            solana_sdk::bpf_loader::id(),
+        )
+    };
+}
+
+use solana_bpf_loader_api::process_instruction;
+solana_sdk::solana_entrypoint!(process_instruction);