Feat: FlashblocksBundle as a specialized FlashbotsBundle

`FlashblocksBundle` in flashblocks and [`FlashbotsBundle`](https://github.com/flashbots/rblib/blob/fc9a7077c1902f0fa0078b50f9e9ebec3b824196/src/platform/bundle.rs#L196) in dependency rblib share lots of same logic.

It would be nice to define FlashblocksBundle as a specialized implementation of FlashbotsBundle, i.e. `FlashblocksBundle = FlashbotsBundle`

There are slight differences such as single target block number / min_block_number and max_block_number.
If necessary we could make `FlashbotsBundle` more generic as a trait with some default impl, provide a `FlashbotsEthBundle` in rblib (same as current FlashbotsBundle), and be able to easily implement FlashblocksBundle here. It could make support of different bundle versions easier. In that case we can move this issue to rblib.