fix(store/genesis): use Smt to compute account root of genesis block

[kkovaacs]

LargeSmt is pretty expensive to construct and since the account tree in the genesis block is not expected to be huge we can safely avoid that initialization cost by simply using Smt instead of LargeSmt.

[Mirko-von-Leipzig]

Oh that's neat.

[bobbinth]

Looks good! Thank you!

Is there a noticeable difference for how fast the tests run with this?

[kkovaacs]

Looks good! Thank you!

Is there a noticeable difference for how fast the tests run with this?

Yes. For example, running all tests for the validator on my laptop before the change:

➤ /usr/bin/time ../../target/debug/deps/miden_validator-014f46be61300bbb 

running 12 tests
test db::migrations::tests::diesel_schema_is_in_sync_with_migrations ... ignored, requires diesel CLI; CI runs this in the diesel-schema job
test db::migrations::tests::migration_schema_hashes_are_stable ... ok
test server::tests::commitment_mismatch_rejected ... ok
test server::tests::chain_tip_plus_one_succeeds ... ok
test server::tests::empty_block_succeeds ... ok
test server::tests::unknown_transactions_rejected ... ok
test server::tests::validate_block_number_mismatch ... ok
test server::tests::chain_tip_plus_two_rejected ... ok
test server::tests::chain_tip_replacement_succeeds ... ok
test server::tests::chain_tip_minus_one_rejected ... ok
test server::tests::new_block_after_replacement_with_stale_commitment_rejected ... ok
test server::tests::replacement_commitment_mismatch_rejected ... ok

test result: ok. 11 passed; 0 failed; 1 ignored; 0 measured; 0 filtered out; finished in 14.26s

24.59user 89.58system 0:14.29elapsed 798%CPU (0avgtext+0avgdata 11525380maxresident)k
23976inputs+0outputs (1784914major+4582167minor)pagefaults 0swaps

After the change:

➤ /usr/bin/time ../../target/debug/deps/miden_validator-014f46be61300bbb

running 12 tests
test db::migrations::tests::diesel_schema_is_in_sync_with_migrations ... ignored, requires diesel CLI; CI runs this in the diesel-schema job
test db::migrations::tests::migration_schema_hashes_are_stable ... ok
test server::tests::unknown_transactions_rejected ... ok
test server::tests::new_block_after_replacement_with_stale_commitment_rejected ... ok
test server::tests::chain_tip_plus_one_succeeds ... ok
test server::tests::empty_block_succeeds ... ok
test server::tests::commitment_mismatch_rejected ... ok
test server::tests::chain_tip_plus_two_rejected ... ok
test server::tests::validate_block_number_mismatch ... ok
test server::tests::chain_tip_minus_one_rejected ... ok
test server::tests::chain_tip_replacement_succeeds ... ok
test server::tests::replacement_commitment_mismatch_rejected ... ok

test result: ok. 11 passed; 0 failed; 1 ignored; 0 measured; 0 filtered out; finished in 0.02s

0.04user 0.01system 0:00.02elapsed 309%CPU (0avgtext+0avgdata 20320maxresident)k
0inputs+0outputs (0major+2322minor)pagefaults 0swaps