v1.16: Remove inappropriate use of usize. Refactor upcast. (backport of

#32539) (#32561)

Remove inappropriate use of usize. Refactor upcast. (#32539)

* Remove inappropriate use of usize. Refactor upcast.
Co-authored-by: Trent Nelson <trent.a.b.nelson@gmail.com>

(cherry picked from commit 83ac15d)

Co-authored-by: Will Hickey <will.hickey@solana.com>

program-runtime/src/compute_budget.rs

@@ -176,7 +176,7 @@ impl ComputeBudget {
         enable_request_heap_frame_ix: bool,
         support_set_loaded_accounts_data_size_limit_ix: bool,
     ) -> Result<PrioritizationFeeDetails, TransactionError> {
-        let mut num_non_compute_budget_instructions: usize = 0;
+        let mut num_non_compute_budget_instructions: u32 = 0;
         let mut updated_compute_unit_limit = None;
         let mut requested_heap_size = None;
         let mut prioritization_fee = None;
@@ -255,18 +255,19 @@ impl ComputeBudget {
             self.heap_size = Some(bytes as usize);
         }
 
-        self.compute_unit_limit = if default_units_per_instruction {
+        let compute_unit_limit = if default_units_per_instruction {
             updated_compute_unit_limit.or_else(|| {
                 Some(
-                    (num_non_compute_budget_instructions as u32)
+                    num_non_compute_budget_instructions
                         .saturating_mul(DEFAULT_INSTRUCTION_COMPUTE_UNIT_LIMIT),
                 )
             })
         } else {
             updated_compute_unit_limit
         }
         .unwrap_or(MAX_COMPUTE_UNIT_LIMIT)
-        .min(MAX_COMPUTE_UNIT_LIMIT) as u64;
+        .min(MAX_COMPUTE_UNIT_LIMIT);
+        self.compute_unit_limit = u64::from(compute_unit_limit);
 
         self.loaded_accounts_data_size_limit = updated_loaded_accounts_data_size_limit
             .unwrap_or(MAX_LOADED_ACCOUNTS_DATA_SIZE_BYTES)