Merge InstructionError and ProgramError

From the user's perspective, it's just an instruction error.
For program-specific errors, we still have
InstructionError::CustomError.

programs/noop/src/lib.rs

@@ -1,8 +1,8 @@
 use log::*;
 use solana_sdk::account::KeyedAccount;
-use solana_sdk::native_program::ProgramError;
 use solana_sdk::pubkey::Pubkey;
 use solana_sdk::solana_entrypoint;
+use solana_sdk::transaction::InstructionError;
 
 solana_entrypoint!(entrypoint);
 fn entrypoint(
@@ -10,7 +10,7 @@ fn entrypoint(
     keyed_accounts: &mut [KeyedAccount],
     data: &[u8],
     tick_height: u64,
-) -> Result<(), ProgramError> {
+) -> Result<(), InstructionError> {
     solana_logger::setup();
     info!("noop: program_id: {:?}", program_id);
     info!("noop: keyed_accounts: {:#?}", keyed_accounts);