perf: cache repeated storage trie lookups

[Qumeric]

Add one-entry caches for address hashes and storage-trie references in WitnessDb. REVM storage accesses commonly arrive in runs for the same account, so this avoids repeated address Keccak operations and storage-trie hash-table lookups without adding a general-purpose cache.

WitnessDb borrows the backing Ethereum state immutably, so cached trie references cannot become stale during execution.

Benchmark results

Block 24001988, execute-metered, develop-v2.1.0 vs this PR:

metric	develop-v2.1.0	this PR	delta
execute_metered_insns	588,618,511	585,948,254	−2,670,257 (−0.454%)
metered_rows_unpadded	844,070,559	838,480,858	−5,589,701 (−0.662%)
metered_main_cells_unpadded	43,260,383,096	42,788,778,698	−471,604,398 (−1.090%)
metered_interaction_cells_unpadded	13,194,454,796	13,132,564,727	−61,890,069 (−0.469%)
metered_memory_unpadded_bytes	713,961,114,662	711,203,678,744	−2,757,435,918 (−0.386%)
app segments	65	64	−1

Cells fall about twice as far as instructions, and the block crosses a segment boundary, because the work being skipped is trie resolution — memory traffic rather than arithmetic.