Resolve issue with unused tx_number field in block structure

[namitkrarya]

Description of the Change

IR157 An un-used variable tx_number was present in the block schema.

Benefits

Less space will be used by a block.

Possible Drawbacks

None

[luckychess]

Hi, @namitkrarya. Congratulations on your first Iroha PR! Your idea is very sensible. Unfortunately, we have at least two reasons not to make that change right now:

• Removing a field from block is a backward-incompatible change (since block's hashes become different) and prefer to avoid them at this point, at least before we make Iroha fully backwards compatible with different block versions (v2 in this case).
• Another mechanism for limiting amount of transactions in a block should be designed. It could be a stateless validation rule of something different. At the moment we are not sure.

Thank you for mentioning that, it does seem outdated. But we need to have a discussion about how to make the change and what alternative design to use.