Rename native_program.rs to instruction_processor_utils.rs

Prefer the term "instruction processor" over "program". Reserve
the term "native" for the loader and shared object it loads.
Compiling an instruction processor to BPF shouldn't imply changing
to a non-native entrypoint.

sdk/src/native_loader.rs

@@ -14,7 +14,7 @@ pub fn check_id(program_id: &Pubkey) -> bool {
 }
 
 /// Create an executable account with the given shared object name.
-pub fn create_program_account(name: &str) -> Account {
+pub fn create_loadable_account(name: &str) -> Account {
     Account {
         lamports: 1,
         owner: id(),