feat: add BAL (Block Access List) example

[mattsse]

Demonstrates EIP-7928 Block Access List usage:

• Phase 1: Build BAL by executing transactions with with_bal_builder()
• Phase 2: Use built BAL for re-execution with with_bal()

The example uses a simple counter contract to show how storage writes are captured and indexed by transaction in the BAL.

Example output

=== Block Access List (BAL) Example ===

--- Phase 1: Building BAL ---
  TX 1: Counter incremented (0 -> 1), gas used: 43126
         Returned value: 1
  TX 2: Counter incremented (1 -> 2), gas used: 26026
         Returned value: 2

  Built BAL with 3 accounts tracked

=== Block Access List (BAL) ===
...
  Storage:
    Total slots: 1
    Slot: 0x0
      Writes:
        [1] -> 1
        [2] -> 2
...

--- Phase 2: Re-executing with BAL ---
  TX 1 replayed with BAL, gas used: 43126
         Returned value: 1
  TX 2 replayed with BAL, gas used: 26026
         Returned value: 2

=== BAL Example Complete ===

[codspeed-hq]

Merging this PR will not alter performance

✅ 173 untouched benchmarks

---

_{Comparing mattsse:feat/bal-example (9d288d8) with main (26785fc)}

[rakita]

fmt pending