chore: Split apply_block

[sergerad]

Splits the apply_block fn to add more instrumentation

rpc [ 3.48ms | 0.00% / 100.00% ] rpc.service: "store.BlockProducer" | rpc.method: "ApplyBlock"
┕━ apply_block [ 3.48ms | 0.00% / 100.00% ]
   ┝━ validate_block_header [ 1.43ms | 41.18% ]
   ┝━ compute_tree_mutations [ 1.14ms | 32.69% ]
   ┝━ build_note_records [ 12.5µs | 0.36% ]
   ┝━ store.block_store.save_block [ 63.2µs | 1.82% ] block_num: BlockNumber(8) | block_size: 357
   ┝━ await_db_readiness [ 12.2µs | 0.35% ]
   ┝━ acquire_inner_write_lock [ 9.62µs | 0.28% ]
   ┝━ apply_block [ 802µs | 13.59% / 23.06% ]
   │  ┝━ insert_block_header [ 88.3µs | 2.54% ]
   │  ┝━ upsert_accounts [ 5.08µs | 0.15% ]
   │  ┝━ insert_scripts [ 18.3µs | 0.53% ]
   │  ┝━ insert_notes [ 14.6µs | 0.42% ]
   │  ┝━ insert_transactions [ 13.4µs | 0.38% ]
   │  ┝━ insert_nullifiers_for_block [ 71.5µs | 2.06% ]
   │  ┕━ acquire_write_lock [ 118µs | 3.40% ]
   ┝━ acquire_forest_write_lock [ 9.12µs | 0.26% ]
   ┕━ ｉ [info]: apply_block successful | block_commitment:

[Mirko-von-Leipzig]

This looks much better thanks, I'm leaving a review now since I'll be on leave soon.

If we can get this in, and then investigate why things are slow that would be fantastic.