`DataAvailabilityMode` should implement `Into<u32>`

[tdelabro]

https://docs.starknet.io/documentation/architecture_and_concepts/Network_Architecture/transactions/#v3_hash_calculation

The doc states that while computing the hash of a tx v3 the DataAvailabilityMode should be represented as a u32 and concatenated inside a Felt.

It would be handy to have this method coming with the lib.
Right now I have to do

nonce_data_availability_mode as u32

This implies a silent overflow if the DataAvailabilityMode internal happens to be greater than a u32.
I know it is not the case, but, as a lib user, I shouldn't have to ask the question and go check the code myself.