refactor(tests): replace manual intrinsic gas arithmetic broken by EIP-7976/EIP-7981 repricing

## Description

Several tests manually compute gas budgets by dividing available gas by raw constants from `fork.gas_costs()` (e.g. `G_ACCESS_LIST_ADDRESS`, `G_TX_DATA_FLOOR_TOKEN_COST`, `PER_EMPTY_ACCOUNT_COST`). This pattern breaks when a new fork reprices these costs, which is what happens in Amsterdam with EIP-7976 (calldata repricing) and EIP-7981 (access list repricing).

Related to #2049 (migration from `fork.gas_costs` to `bytecode.gas_cost(fork)`), that issue covers opcode-level gas costs, while this tracks intrinsic transaction gas calculations that should use the fork's `intrinsic_cost()` calculator via binary search instead of manual division.

## Anti-pattern

```python
gas_available = some_limit - intrinsic_cost()
count = gas_available // SOME_GAS_CONSTANT
```

## Safe pattern

```python
count = max_count_with_intrinsic_cost_at_most(
lambda n: intrinsic_cost(..., n),
some_limit,
)
```

## Already fixed

- `test_tx_gas_limit_cap_access_list_with_diff_keys` (#2250)
- `test_tx_gas_limit_cap_access_list_with_diff_addr` (#2250)
- `test_tx_gas_limit_cap_authorized_tx` (#2250)
- `test_tx_gas_limit_cap_full_calldata` (#2250, #2286)
- `_exact_size_transactions_impl` in EIP-7934 tests (#2252)
- `test_refunds` in EIP-7623 tests (#2252)

## Still unfixed

### EIP-7825 (`tests/osaka/eip7825_transaction_gas_limit_cap/test_tx_gas_limit.py`)
- `test_tx_gas_limit_cap_contract_creation` — `gas_available // total_cost_floor_per_token`
- `test_maximum_gas_refund` — `tx_gas_limit_cap // iteration_cost`

### EIP-7702 (`tests/prague/eip7702_set_code_tx/`)
- `test_gas.py` — `max_gas // Spec.PER_EMPTY_ACCOUNT_COST`
- `test_set_code_txs.py` — `gas_for_delegations // Spec.PER_EMPTY_ACCOUNT_COST`

### Benchmarks (`tests/benchmark/`)
- `test_transaction_types.py` — `gas_amount // total_cost_floor_per_token`, `gas_after_address // gas_per_storage_key`
- `test_system.py` — `(per_tx_gas - intrinsic_cost) // (access_list_addr_cost + cost)`

Start with the listed tests in tests/osaka/eip7825_transaction_gas_limit_cap/test_tx_gas_limit.py, tests/prague/eip7702_set_code_tx/test_gas.py, tests/prague/eip7702_set_code_tx/test_set_code_txs.py, and the benchmark files. Replace each manual gas-constant division with max_count_with_intrinsic_cost_at_most and the relevant intrinsic_cost calculation, then verify the affected tests and benchmarks no longer depend on repriced raw constants.

Written by the indexing model from the issue text.