Charge compute budget for bytes passed via cpi (#15874)

sdk/src/process_instruction.rs

@@ -128,6 +128,8 @@ pub struct BpfComputeBudget {
     pub log_pubkey_units: u64,
     /// Maximum cross-program invocation instruction size
     pub max_cpi_instruction_size: usize,
+    /// Number of account data bytes per conpute unit charged during a cross-program invocation
+    pub cpi_bytes_per_unit: u64,
 }
 impl Default for BpfComputeBudget {
     fn default() -> Self {
@@ -149,6 +151,7 @@ impl BpfComputeBudget {
             stack_frame_size: 4_096,
             log_pubkey_units: 100,
             max_cpi_instruction_size: 1280, // IPv6 Min MTU size
+            cpi_bytes_per_unit: 250,        // ~50MB at 200,000 units
         }
     }
 }