add checked instructions sysvar api (backport #20790) (#20816)

* add checked instructions sysvar api (#20790)

(cherry picked from commit a8098f37d0)

# Conflicts:
#	programs/bpf/rust/sysvar/src/lib.rs
#	runtime/src/accounts.rs

* resolve conflicts

Co-authored-by: Jack May <jack@solana.com>

programs/bpf/rust/instruction_introspection/src/lib.rs

@@ -26,9 +26,9 @@ fn process_instruction(
         return Err(ProgramError::InvalidAccountData);
     }
 
-    let instruction = instructions::load_instruction_at(
+    let instruction = instructions::load_instruction_at_checked(
         secp_instruction_index as usize,
-        &instruction_accounts.try_borrow_data()?,
+        instruction_accounts,
     )
     .map_err(|_| ProgramError::InvalidAccountData)?;