Add `transaction_index` Scanner Field to Scanners That Rely on `from_block`

sync::from_block and historic builders would have the additional optional transaction_index builder function, that would allow devs to specify the exact transaction index in the from_block from which to start streaming.

let mut scanner = EventScannerBuilder::sync()
    .from_block(100)
    .transaction_index(5)
    .connect(provider)
    .await?;

// this means: "start streaming from block 100, discarding all logs prior to transaction index 5"

// Historical block range mode
let scanner = EventScannerBuilder::historic()
    .from_block(1000)
    .transaction_index(15)
    .to_block(2000)
    .max_block_range(500)
    .connect(provider.clone());

// "stream logs from block 1000 to block 2000, discarding all logs prior to transaction index 15"

• DEFAULT_TRANSACTION_INDEX = 0
• if the set transaction index is higher than the number of transactions that the specified block contains, the scanner would skip the whole block completely.

Start by locating the EventScannerBuilder::sync and EventScannerBuilder::historic implementations and their from_block handling. Add the optional transaction_index behavior described in the issue, including the default of 0 and skipping blocks when the index is out of range; done means both scanner modes honor the requested starting transaction.